7 Must-Add Waiver Wire Pickups for Week 20 Fantasy Baseball (2026)

August 8, 2026

Frank breaks down his must-add fantasy baseball waiver wire pickups for Week 20 of the 2026 MLB season. Add these players now off the waiver wire and win more.

Hello, RotoBallers! Welcome back to another edition of our 7 Must-Adds ahead of Week 20 of the fantasy baseball season. We've got another intriguing prospect who has been called up to the big leagues.

This week, we will spotlight seven players who are available in more than 75% of all Yahoo leagues and explain why managers should prioritize them on the waiver wire. Be sure to follow RotoBaller MLB on X for all of our league-winning content and me @FAmmiranteTFJ.

Additionally, be sure to use discount code FRA for 50% off any Premium Packages and gain access to our Team Sync platform with customized lineup tools, projections, and more based on your league settings. Let's dive in!

2026 Fantasy Baseball Week 20 Waiver Wire Adds

Kade Anderson, SP, Seattle Mariners

22% rostered

Kade Anderson is the consensus top pitching prospect in MLB right now. The Mariners lefty came into Friday's action on a completely dominant run in the minors. Anderson has a 1.20 ERA and a 0.66 WHIP with a 40.5% strikeout rate and a 4.1% walk rate in 82.1 innings at Double-A. Simply put, those are video game numbers. It's clear that Anderson is ready for the big leagues.

We saw him continue to dominate on Friday night, tossing 5.1 scoreless innings with zero walks and nine strikeouts.

Kade Anderson strikes out the side in the top of the first. 13 pitches, 11 strikes, 6 whiffs. pic.twitter.com/zPRb9k3PMV

— Mariners Minors (@MiLBMariners) August 8, 2026

The Mariners are currently 56-60 as of Friday night, so they definitely need a spark to ignite the team for the stretch run. Otherwise, they're going to miss the playoffs. What better way to do that than call up Anderson?

After trading Luis Castillo, that opens up a spot in the rotation. They can bring up Anderson and go back to a six-man rotation. It's also worth noting that both Emerson Hancock and Bryce Miller have fallen off after strong starts.

In Hancock's last eight starts, he has a 4.43 ERA and a 1.30 WHIP in 40.2 innings. In Miller's last five starts, he has a 5.81 ERA and a 1.52 WHIP in 26.1 innings. It's clear that they can use Anderson.

What's encouraging is that the M's have publicly stated that once Anderson is up, he'll be starting rather than deployed out of the bullpen. With that in mind, it's only a matter of time before this potential difference-maker is up in Seattle.

Andruw Monasterio, 1B/2B/3B/SS, Boston Red Sox

17% rostered

Andruw Monasterio has been quite the surprise contributor for the red-hot Red Sox, slashing .268/.322/.460 with six home runs and three stolen bases in 234 plate appearances. But the season-long numbers don't even tell the whole story. Heading into Friday night, Monasterio was slashing .345/.406/.607 with three homers and two steals in 97 plate appearances.

Even though Monasterio has been hitting between the 6 to 8 spot in the Red Sox lineup, he's been able to provide a major boost to your batting average. It feels like everyone on this team is in lockstep right now, each in a hot streak at the same time. That means it's a good idea to just pick up Monasterio and ride the wave.

ANDRUW MONASTERIO WITH AN RBI OFF THE MONSTER pic.twitter.com/3oJ8a2wXIs

— NESN (@NESN) August 7, 2026

You also have to like the favorable schedule for next week, as the Red Sox are one of the few teams with seven games on tap. This includes four games at the Blue Jays and three at the Pirates.

With Monasterio swinging the bat so well, he's worth a look, especially since he's eligible at four positions across the infield.

Jacob Webb, RP, Chicago Cubs

15% rostered

Jacob Webb has been rock-solid for the Cubs this year, registering a 2.49 ERA and a 1.20 WHIP with a 26.5% strikeout rate and an 8.1% walk rate in 50.2 innings. The numbers are supported by the underlying metrics, including a 3.24 SIERA.

We've seen Webb convert saves on August 5th and August 7th, so it's clear he's the top option for saves, even though the Cubs acquired Ryan Zeferjahn at the deadline.

With Danny Palencia still a week or two away, it makes sense to pick up Webb if you're desperate for saves. Remember, there's a chance that Palencia will be eased back into the role once he returns, especially since he's coming off an extended absence.

Webb is so widely available in leagues, so he's worth a look.

Kaelen Culpepper, SS, Minnesota Twins

7% rostered

Kaelen Culpepper was finally called up to the big leagues, making his debut on August 7th. This is a 23-year-old shortstop who slashed .271/.367/.478 with 14 home runs and 17 stolen bases in 343 plate appearances.

There's a nice power and speed profile here, so I recommend picking up Culpepper immediately to see where this goes. Remember, rookies have unknown ceilings. They can blow expectations out of the water, especially in short spurts. Just look at what Esmerlyn Valdez did in Pittsburgh earlier this year.

Culpepper hit seventh in his MLB debut, but there's opportunity for him to move up in the order, especially when he does things like this:

WELCOME TO THE SHOW KAELEN CULPEPPER pic.twitter.com/Mn0ETtRPEw

— Minnesota Twins (@Twins) August 8, 2026

The rookie shortstop went 1-for-4 with a solo home run in his debut. Pick him up before it's too late.

Tyler Mahle, SP, Atlanta Braves

7% rostered

Tyler Mahle has been intriguing in his last three starts. He pitched six scoreless innings against the Brewers. After that, even though he allowed five earned runs vs. the Padres, it came with nine strikeouts. Then on Friday, in Mahle's debut with the Braves, he tossed six scoreless innings with nine strikeouts against the Yankees.

Mahle is showing increased velocity. Now that he's pitching for a contender, we could see a strong finish to the season, especially since the Braves have done a good job getting more value out of their pitchers.

Playing for Atlanta means more opportunities for wins, giving Mahle more fantasy value. Up next is a home matchup against the Mets, so we could see a quality outing there as well.

With Mahle so widely available in leagues, he's easy to grab right now.

Ben Joyce, RP, Los Angeles Angels

5% rostered

The Angels traded Ryan Zeferjahn and Kirby Yates at the trade deadline, creating a wide-open spot in the ninth. This gives Ben Joyce an opportunity to claim the closer role.

He pitched a scoreless and hitless inning in relief against Baltimore on August 5th, hitting 102.2 MPH in that game. It's clear that he still has the velocity to make an impact in the closer role.

If you're in a deep league desperate for saves with room to stash Joyce, I recommend giving him a look.

Cody Bradford, SP, Texas Rangers

3% rostered

Cody Bradford looked sharp in his return to action, tossing 4.1 scoreless innings against the Giants. The Rangers are in a pitcher's park, so it's the ideal environment for Bradford.

Playing for a team in the AL Wild Card hunt, Bradford will have a chance to make an impact. Remember that he put up a 3.54 ERA and a 1.01 WHIP in 76.1 innings back in 2024.

There's some upside here. As he works his way up, he can provide strong ratios for you, so I'd pick him up in deeper leagues.

Other Fantasy Baseball Waiver Wire Targets

• Cade Povich, BAL
• Osleivis Basabe, SFG
• Colt Keith, DET
• Trevor Larnach, MIN
• Jake Mangum, PIT
• Nolan Schanuel, LAA
• Angel Martinez, CLE
• Mason Montgomery, PIT

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