RotoBaller Staff Roundtable - Waiver Wire Pickups: Fantasy Baseball Week 21

August 15, 2026

RotoBaller staff's fantasy baseball Week 21 waiver wire pickups for 2026. Expert advice for waiver wire hitter, pitcher, and closer targets from Andy, Kevin, and Marty.

Welcome, RotoBallers, to another staff roundtable ahead of Week 21 of the fantasy season. As always, we will spotlight our top waiver wire targets from members of our fantasy baseball staff, including Andy Smith, Kevin Larson, and Marty Tallman.

In this week's edition, we will spotlight several recent prospect call-ups, including a rising star in Colorado and several options for those looking for saves.

Who should we look to pick up this week? Let's dive in!

Hitter Fantasy Baseball Waiver Wire Pickups

Griffin Conine, OF, Miami Marlins

Conine may be one of the players I'm highest on in the league right now. I wrote about him a couple weeks ago in my Breakouts vs Fake Outs article, and I've loved what he's done since. Over the last 14 days, he's smashing for a 194 wRC+. That's a .462 wOBA and a .465 xwOBA, even with a 28.3% strikeout rate. A 56.0% hard-hit rate and a 24.0% barrel rate in that span will really help get you results.

GRIFFIN CONINE IS SIZZLING ♨️ pic.twitter.com/EZ0ZcJNICj

— Miami Marlins (@Marlins) August 13, 2026

His seven runs and seven RBI are tied for the Marlins' lead in that span, making him one of their more important players. He's simply finding every way to contribute, even with a 17.4% walk rate. If you're looking for a guy that could be a game-changer down the stretch, then get Conine on your roster.

- Eric Cross

Nolan Arenado, 3B, Arizona Diamondbacks

I mentioned Arenado as a waiver wire target a few weeks ago, and he's still sitting at a lowly 28% rostered number. With his recent production and the overall effectiveness of Arizona's lineup, he absolutely should be on more rosters. He's hitting for a 133 wRC+ over the last 14 days, fueled by a 10.0% walk rate and four homers.

The 35-year-old has been the ninth-best fantasy producer at third base over those two weeks. His production levels should continue to stay high. After an early-week series at Fenway, he'll get tasty matchups against the Reds back at Chase Field.

- Kevin Larson

Tim Tawa, 1B/2B/3B/OF, Arizona Diamondbacks

On the season, the utility man carries a .232/.284/.379 line with a modest .663 OPS. He has gone deep six times and chipped in another six stolen bases.

However, his recent play at the dish has pushed him onto this piece.

Since August 2 (his last 11 games), Tawa has carried a sharp .310/.333/.452 line with two of these home runs and four of his six stolen bases. Prior to this surge, Tawa rarely had consistent at-bats in the majors and had a modest .715 OPS over his last 22 contests.

While his track record of success is not only large, Tawa has become a lineup regular in Arizona, which makes him worth a closer look ahead of Week 21.

The major surge in his power has been on display across all three pitch types. As shown in the visual below, Tawa has seen his xSLG across all three pitch types increase over the past month compared to his production in the opening months of the season.

The other aspect of his profile that is promising to managers is his Pull AIR%. Seeing his power begin to show on the box score (two home runs over his last 10 games) is very promising, and the underlying 17.3% Pull AIR% can open the door for a greater second-half surge.

When in the minor leagues, Tawa hit 31 home runs back in the 2024 season (142 games) and hit seven long balls over a 20-game stint in Reno this season.

- Andy Smith

Joshua Baez, OF, St. Louis Cardinals

Don't look now, but outfielder Joshua Baez is only five home runs away from the Triple-A record of 38.

Joshua Báez extends his Triple-A HR lead with a 112.7 MPH ROCKET 🚀

The @Cardinals' No. 3 prospect tallies his 33rd long ball of the season for the @memphisredbirds: pic.twitter.com/glOPfoOiVV

— MLB Pipeline (@MLBPipeline) August 8, 2026

Baez has tormented Triple-A pitching this year, hitting .254/.326/.567 with 33 home runs, 88 RBI, 78 runs scored, and 21 stolen bases across 457 plate appearances.

The only thing potentially holding him back is the amount of swing-and-miss in his game. As we have covered extensively this season, Baez strikes out 30% of the time with a 34% chase rate and a 34% whiff rate.

Even with all the punchouts, he's posted a 20% barrel rate (97th percentile) and a ridiculous 115.4 mph max exit velocity, one of the highest marks in the history of the minor leagues.

He also holds a 50% swing rate (80th percentile) and 72% zone swing rate (77th percentile). In other words, if the ball is in the zone, there is a good chance he will crush it.

Also, unlike most top-tier sluggers, he has great baserunning instincts to pair with 92nd-percentile sprint speed.

The 23-year-old should be viewed as a must-add pick up ahead of his MLB debut on Saturday.

- Marty Tallman

Henry Bolte, OF, Athletics

Early in the season, Bolte's name was popping off as a popular add. He had a ton of hype in the minors and started off hot as well. A cold July seems to have kept him off many fantasy managers' radars, but maybe that's a mistake. In August, he's turned it around and is back to hitting for a 138 wRC+, driven by a .310 BA and a couple of homers to boot.

Henry Bolte adds his 5th Home Run of the year to make it 7-2 @Athletics!

🎙️ @JDoskow #MLB #HomeRun #Baseball #Athletics pic.twitter.com/hvQomfmN0q

— A's Cast (@athleticscast24) August 8, 2026

He's added on a couple stolen bases too, helping to showcase his upper-echelon speed. At 4% rostered, you're not going to have much competition for him. So don't overpay for him, but I do think you'll like the results you get in the near-term if he makes it on your roster.

- Kevin Larson

Cam Smith, OF, Houston Astros

The former top prospect may be finally putting it together. Over his last 12 contests (since July 29), the former first-round pick has posted a stellar .386/.413/.682 line with a 1.095 OPS, two doubles, three home runs and a 13:2 K:BB.

Prior to this stretch, Smith held a modest .204/.281/.359 line with 13 long balls over 107 games. While he has shown flashes of potential at times, it appears this recent stretch could be the start of his long-awaited breakout.

The major key to Smith's recent improvements is his increasing pull rates. Smith has always shown impressive raw skill, as evidenced by his 99th-percentile bat speed, but has never had consistent home run totals due to an ineffective pull rate.

However, as shown below, the former Chicago Cub draft pick has begun to pull the ball more effectively when facing breaking balls and fastballs, which has been the catalyst for his recent improvements.

The 23-year-old has also generated a high 11.9% barrel rate with a 45.7% hard-hit rate on the season. If Smith can continue to uphold the ball effectively, the right-hander could become a league-winning down the stretch.

He is a top add in all 12-team formats ahead of Week 21.

- Andy Smith

Zac Veen, OF, Colorado Rockies

Zac Veen made his MLB debut in 2025, but struggled over his limited stint of action. Through his first 12 games in the majors, Veen posted a rough .118/.189/.235 line with a .424 OPS. As a result, Veen was not on the radar of many entering the 2026 season, as he was not expected to earn a role in the major leagues at the time.

While he didn't earn the call until later this season, Veen was among the top hitters in the minor leagues ahead of his promotion. Through 100 games at Triple-A Albuquerque this season, Veen posted an elite .327/.402/.635 line with a 1.037 OPS. During this stretch, the former ninth overall pick from the 2020 MLB Draft hit33 doubles, launched 24 home runs, and even chipped in 18 stolen bases.

Over his last 12 games before earning the call, Veen took his play to another level as he launched eight home runs (including a three-home run effort) with a .462/.533/1.115 line.

While Veen was held out of the lineup for his first few games back in the majors, he wasted little time making an impact in his first start. On Wednesday, Veen went 1-for-3 with a long ball.

Even though Veen may not be given a full-time role, his five-category potential makes him a worth look across all standard leagues this weekend. If he were to carve out a full-time role, he could become a must-start option down the stretch.

COL - Zac Veen 2-run HR (1)

📏 407 ft | 💨 104.7 mph | 📐 26°
⚾️ 86.7 mph changeup (ARI - RHP Merrill Kelly)
🏟️ Out in 29/30 parks

COL (6) @ ARI (1)
🔺 4th#Rockies pic.twitter.com/Y27u4EMgW6

— MLB Home Runs (@MLBHRs_) August 12, 2026

- Andy Smith

Pitcher Fantasy Baseball Waiver Wire Pickups

David Peterson, SP, Chicago Cubs

It hasn't quite been the greatest of seasons for Peterson, but I think the tide may start turning for him with the Cubs here shortly. He's allowed three or fewer ER in each of his last three starts while recording six or more strikeouts in two of them. He's still got some walk issues he's got to get resolved, but the tick up in strikeouts is what's really driving me to view Peterson as a solid fantasy option going forward.

He'll get the rock on Tuesday against the White Sox. While Chicago's offense can produce at a high level, they're more lefty-dominant, and that gives Peterson a bit of a platoon advantage. You don't have to stretch your budget to add Peterson, but I do think he's on the right path to turning things around. Him on your roster, even as a stash, may help you out down the line.

- Kevin Larson

Tyler Mahle, SP, Atlanta Braves

From a full-season perspective, Mahle has been an underwhelming starter. However, it's starting to look like he's getting things turned around over his last few starts. In his last three outings, he's notched 26 strikeouts, adding up to a 37.7% strikeout rate. Two of those starts have come with Atlanta, where he's ultimately increased his chances of recording a win compared to his time in San Francisco.

Tyler Mahle, Dirty 88mph Splitter. ✌️

6th K pic.twitter.com/xwUfMHctcD

— Rob Friedman (@PitchingNinja) August 13, 2026

I'm banking on Mahle being much better with the change of environment in Atlanta. Competitive baseball can do wonders for a player's mindset. He's slated for two starts next week, one against Minnesota and one against Milwaukee. The Brewers matchup is tough, but having two starts gives him a lot of potential for Week 21.

- Kevin Larson

Kade Anderson, SP, Seattle Mariners

Another week, another dominating start by Kade Anderson. Anderson is expected to be called up within the next week, and the Mariners' front office has already said he will be a starter for the rest of the season.

Kade Anderson was awesome again. Final line: 5.1IP, 3H, 0R, 0BB, 9K, 19 whiffs, 78 pitches, 58 strikes.

12th start without allowing a run.

Anderson in his first professional season:
17G, 1.13ERA, 87.2IP, 45H, 12BB, 128K. pic.twitter.com/YshHD76jle

— Mariners Minors (@MiLBMariners) August 8, 2026

In Double-A, Anderson has a 1.13 ERA, a 40.9% strikeout rate, a 38% whiff rate, a 3.8% walk rate, and a 0.65 WHIP across 87 2/3 innings. Simply put, he is the best pitcher in the minor leagues.

From an arsenal standpoint, Anderson has a 70-grade fastball that sits around 92-95 mph. It doesn't have elite velocity, but the carry through the top of the zone helps it play up.

The former LSU standout gets on hitters with a combination of carry, extension, arm speed, and pinpoint location. His slider is another strong pitch, sitting in the mid-80s with good lateral movement.

The velocity also makes it tough for hitters to sit on. His curveball is arguably his best breaking pitch. It's a high-spin, deep-breaking ball with plenty of vertical drop.

He also mixes in a changeup, which he mostly uses against right-handed hitters to keep them off balance.

Once Anderson gets called up, he'll be a must-roster in every fantasy format. He should already be stashed in all leagues, so get him while you still can.

- Marty Tallman

Jacob Webb, Chicago Cubs

Webb has been one of the Cubs' best relievers this year and has been cooking in the second half. He's yet to give up an earned run while posting a 9.26 K/9 since the break. He's also been the Cubs' main guy in the ninth inning, notching three saves in August.

With a wiffle ball changeup, Jacob Webb has been one of the league leaders in whiffs (95th percentile).

Last night, he ended the game with three straight changeups, getting Abrams to whiff on the first two and roll over the last one to Nico.

Webb's ERA is now 2.38. pic.twitter.com/EEwKKcY0zP

— Brendan Miller (@brendan_cubs) August 12, 2026

He's becoming a dominant bullpen arm that's very under-the-radar. At 4% rostered, you're not likely to have much competition in bidding and don't have to stretch your budget. But a little bit of focus on Webb can really help stabilize any of your own bullpen issues your roster may have.

- Kevin Larson

Samy Natera Jr., RP, Los Angeles Angels

With Kirby Yates and Ryan Zeferjahn now off the roster, the Angels bullpen is wide open for the final months of the season. While much of the attention has gone to Ben Joyce, who recently returned to the major leagues and earned a save this week, the name to watch is Samy Natera Jr.

The southpaw made his MLB debut this season and has yet to face any major struggles. Through his first 27 innings, the left-hander has posted a 2.00 ERA with a 0.85 WHIP. Through this stint, he has struck out 42 hitters (40.4% K%) while walking 9.6% of the batters he has faced. While his walk rate could be lower, he is allowing very weak contact.

He has generated a 1.99 xERA and a .147 xBA with a 31.4% hard-hit rate, all of which would place him in the elite tier of relievers if he were to have logged enough innings. His high-end strikeout rate is also quite sustainable, as suggested by the 37.3% whiff rate.

However, what has put him on this list are his recent improvements. While his walk rate on the season remains inflated, his command has been much stronger over the past month. Since June 24 (his last 20 2/3 innings), Natera has held a 34:4 K:BB with a 2.18 ERA and a 0.73 WHIP. Over his last three outings, he has gone 2-for-2 on saves while Joyce has earned just one save (on August 12).

While this could shift to a committee, Natera appears to have the upper hand at the time of writing. His elite strikeout production and declining walk rate will also allow him to provide fantasy value, even if the saves are not overly consistent.

- Andy Smith

Justin Martinez, RP, Arizona Diamondbacks

A name to watch for saves is Justin Martinez of Arizona. Following the release of Paul Sewald, the Diamondbacks have relied on a mix of Brandyn Garcia, Kevin Ginkel, Juan Morillo, and Jonathan Loaisiga to operate in high-leverage situations. While Garcia has emerged as the slight favorite, Martinez appears poised to slide into this role when he heals back from injury.

The right-hander has been on the shelf after undergoing Tommy John surgery, but embarked on a rehab assignment earlier in the second half and is now on the verge of returning to the desert.

Martinez began his rehab assignment with Low-A, where he logged two scoreless frames with a 3:1 K:BB. He then moved up to Triple-A Tacoma, where he tossed another clean frame on August 11 and added another two punchouts.

Back in 2024, Martinez logged a season-high 72 2/3 innings in the desert, where he posted a tidy 2.48 ERA with a 1.31 WHIP. While the 11.7% BB% inflated his WHIP, he flashed high-end strikeout upside, posting a 29.5% K% with light saves. Before hitting the shelf in 2025, Martinez added another five saves while holding an elite 3.21 xERA, .163 xBA, and a 32.8% K%.

Seeing him improve his command in his rehab assignment is a positive sign for his outlook for the remainder of the season. Even though it may take him some time to fully climb the ninth-inning job, Martinez is best equipped to operate as the primary ninth-inning option down the stretch as they look to secure a Wild Card.

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