MLB Prospect Debuts: Fantasy Baseball Waiver Wire Pickups and Rookie Stashes (Week 1)

April 1, 2026

Marty's fantasy baseball prospect stashes, sleepers, rookie waiver wire pickups for Week 1 of 2026 -- recent MLB prospect debuts and potential call-ups to monitor.

The MLB season is in full swing, which means it’s time to start perfecting your fantasy roster. In this article each week, we are going to highlight prospects who have either just been called up or are excelling in the minors and could see a promotion soon. For this first week, we’ll highlight mostly rookie hitters and pitchers who began the season on a major league roster. All players discussed are under 60% rostered in Yahoo! leagues.

In 2026, there’s a massive wave of rookies beginning the year with their big league clubs due to new service-time rules, which incentivize teams to promote their top prospects earlier. For fantasy managers, this makes it more important than ever to stay on top of emerging talent. Of course, it’s still very early in the season, and we’re working with a small sample size, but these rookies offer the upside that could have an immediate impact on your fantasy roster.

Some of these young players will inevitably be sent back down or become drop candidates within a few weeks, but if you want to strike prospect gold, you have to be willing to take risks and bet on tools and talent. If you have any comments or questions, feel free to message me on X @Marty _Tallman. Now, let’s take a look at some of the best prospect waiver wire pickups and rookie stashes.

• Fantasy baseball draft kit
• Fantasy baseball rankings
• Team Sync platform and Draft Assistant
• Fantasy baseball mock draft simulator
• Fantasy baseball draft cheat sheets
• Fantasy baseball closer depth charts
• Fantasy baseball prospects

Fantasy Baseball Hitter Prospects To Target

Samuel Basallo, C, Baltimore Orioles (38% rostered)

Level: MLB

2026 Stats: 12 PA, .200/.333/.200, 2 R, 0 HR, 0 RBI, 0 SB, 33.3 K%, 16.7 BB%, 45 wRC+

Although it may not look like it right now, Samuel Basallo has the upside to finish as a top-12 fantasy catcher this season. Basallo is currently in a strong-side platoon role, serving primarily as the Orioles’ DH while hitting in the middle of the lineup. He will also fill in for Adley Rutschman when he needs a break behind the dish. Basallo's raw power and elite bat speed give him legitimate 25-home run upside, especially when you consider what he accomplished in the minors.

Here’s a look at his Triple-A Prospect Savant page. Notice all the bright, glowing red.

At Triple-A in 2025, he hit 23 home runs while slashing .270/.377/.589 across 321 plate appearances. He also maintained an above-average walk rate while keeping his strikeout rate at a respectable level. Unfortunately, after being called up by the O's late in the season, Basallo struggled to find immediate success, hitting just four home runs with a .330 slugging percentage over 118 plate appearances.

However, he also posted a .187 BABIP, suggesting he may have been a bit unlucky in his short MLB stay.

In 2026, he hasn’t fully settled in yet, but the upside is too strong to ignore at the catcher position. Basallo is rosterable in all 12-team leagues.

Carson Benge, OF, New York Mets (37% rostered)

Level: MLB

2026 Stats: 16 PA, .214/.313/.429, 3 R, 1 HR, 1 RBI, 2 SB, 12.5 BB%, 31.3 K%, 116 wRC+ 

Carson Benge won the starting job out of camp and is currently working as the primary right fielder. Benge is a dynamic outfielder who has a mature plate approach, solid contact skills, and above-average speed. Across three levels in 2025, the 22-year-old hit 15 home runs and stole 22 bases, slashing .281/.385/.472 over 519 plate appearances.

He also impressed during spring training, collecting 15 hits in just 46 plate appearances while flashing his glove in right field.

What a play in right field by Carson Benge! pic.twitter.com/XSwiXBrNAN

— SNY Mets (@SNY_Mets) February 27, 2026

Looking ahead to 2026, Benge has the skill set to hit 15 home runs, steal 20 bases, and post a .245 batting average. He’s best suited for deeper 12-team leagues right now, but he should absolutely be on your radar in case he takes a step forward and fully breaks out.

Justin Crawford, OF, Philadelphia Phillies (23% rostered)

Level: MLB

2026 Stats: 22 PA, .333/.400/.333, 2 R, 0 HR, 0 RBI, 0 SB, 10 BB%, 30 K%, 116 wRC+ 

Justin Crawford is the everyday center fielder in Philly, and he brings elite speed and a solid hit tool, which should lead to plenty of stolen bases and a decent batting average. At Triple-A last season, Crawford hit seven home runs and stole 46 bases, finishing with the third-most steals at the level. Unfortunately, when you take a look at his barrel rate and pull percentage, you can see why you shouldn't expect him to hit more than 10 home runs in a single season.

Even though the 22-year-old is mostly batting ninth, when he does get on base, he’s turning the lineup over to Trea Turner, Kyle Schwarber, and Bryce Harper. For 2026, the left-handed hitter projects to hit under double-digit home runs but swipe nearly 30 bases, and carry a .250 batting average. Even if he doesn’t find immediate success at the plate, his defense should help keep him in the lineup.

Crawford is rosterable in 12-team leagues, especially if you’re looking to add speed to your roster.

Carter Jensen, C, Kansas City Royals (23 % rostered)

Level: MLB

2026 Stats: 13 PA, .091/.154/.364, 1 R, 1 HR, 2 RBI, 0 SB, 7.7 BB%, 38.5 K%, 33 wRC+ 

Carter Jensen is another up-and-coming catcher with a strong bat. Jensen will DH and back up aging veteran Salvador Perez, which should lead to over 550 plate appearances in 2026. Jensen quickly climbed through the Royals’ system in 2025, earning a call-up at just 22 years old. Once in the majors, he did not disappoint.

Over 69 plate appearances, he hit three home runs while barreling the ball 20.8% of the time. If he qualified, that barrel rate would have tied Phillies’ slugger Schwarber for fourth in MLB. He also showed strong plate discipline, walking 13% of the time and posting a 77.5% contact rate. For 2026, Jensen has the profile to hit 20 home runs, while swiping a handful of stolen bases and carrying a solid batting average, giving him top-12 fantasy catcher upside if he reaches full playing time.

However, that upside is not a guarantee. If he continues to struggle, his playing time will be something to monitor closely as we progress through April.

Owen Caissie, OF, Miami Marlins (18% rostered)

Level: MLB

2026 Stats: 14 PA, .385/.429/.769, 2 R, 1 HR, 4 RBI, 1 SB, 7.1 BB%, 21.4 K%, 231 wRC+ 

In the offseason, the Marlins traded veteran pitcher Edward Cabrera for 23-year-old outfield prospect Owen Caissie. Caissie is a left-handed power hitter with strong offensive upside, but he has a lot of swing-and-miss in his game.

Owen Caissie (acquired by MIA) is a big-power Top 100 prospect who slugged his way through AAA with exceptional quality of contact metrics and a solid approach. He projects to be a solid corner outfield, but his profile is plagued by poor contact rates, especially against spin https://t.co/dsiTvC5rkf pic.twitter.com/zoDM9ciIGR

— Thomas Nestico (@TJStats) January 7, 2026

In 2025, Caissie posted a 28% strikeout rate in Triple-A and an elevated 40.7% strikeout rate in the majors, so caution is warranted. For 2026, he is expected to serve as a strong-side platoon bat, and he’s currently off to a hot start. Caissie should be rosterable in deep 12-team leagues, and if his production cools, he’s an easy cut.

TJ Rumfield, 1B, Colorado Rockies (4% rostered)

Level: MLB

2026 Stats: 16 PA, ..357/.438/.643, 3 R, 1 HR, 3 RBI, 0 SB, 12.5 BB%, 25 K%, 190 wRC+

Now, be honest, had you heard of T.J. Rumfield before this week? Rumfield is the primary first baseman for the Rockies, and he’s getting everyday at-bats. He combines strong contact skills with just enough power to turn doubles into home runs in Coors Field. In Triple-A last year, while in the New York Yankees organization, Rumfield hit 15 home runs with 77 runs, 73 RBI, and five stolen bases, slashing .285/.378/.447 across 587 plate appearances.

He also maintained a 12% walk rate and an 18.4% strikeout rate.

For 2026, the hope is that Rumfield can unlock another level of power or at least adjust his launch angle to hit more fly balls at home. Early signs are promising: his launch angle has increased from 10.5 degrees in 2025 to 17 degrees in 2026, along with a career-low ground-ball rate. Small sample sizes, yes, but this is exactly the kind of adjustment fantasy managers love to see.

Rumfield is rosterable in 15-team leagues and makes a solid streaming option in 12-team leagues when he’s playing at home.

Fantasy Baseball Pitcher Prospects To Target

Parker Messick, SP, Cleveland Guardians (26% rostered)

Level: MLB

2026 Stats: 6 IP, 0.00 ERA, 0.83 WHIP, 25 K%, 0 BB%

Parker Messick is a left-handed, command-first pitcher who excels at mixing a deep arsenal of pitches. Last year, he showcased one of the best changeups in the minors, while his low-90s fastball plays up thanks to deception and natural carry. To start the 2026 season, Messick tossed a gem against the defending world champion Los Angeles Dodgers, demonstrating why he’s one of the top pitching prospects on most waiver wires.

Parker Messick ‼️

6 IP, 5 H, 5 K, 0 ER, 0 BB... of yeah, against the DODGERS.

10 whiffs
21% CSW

Absolutely worth a look in all 12-team-or-more formats, if available. pic.twitter.com/ShPi0DVaj6

— Nicho Roessler (@NichoRoessler) March 31, 2026

In Triple-A in 2025, the 25-year-old posted a 3.47 ERA with a 29.1% strikeout rate across 98 2/3 innings. While we shouldn’t expect that strikeout rate to fully carry over to the majors, he should settle around 25%, which is still very serviceable. Over the next couple of months, Progressive Field in Cleveland is likely to play as a pitcher-friendly park, so consider selling high on Messick around June if he’s at his peak.

Even if you hold him, target favorable matchups, particularly at home during the colder months. If he struggles, he’s an easy option to send down, as he still has three minor league options remaining. Messick is rosterable in all 12-team leagues.

Jonah Tong, SP, New York Mets (6% rostered)

Level: Triple-A 

2026 Stats: 4 IP, 0.00 ERA, 0.75 WHIP, 26.7 K%, 13.3 BB%

Jonah Tong is one of the most exciting pitching prospects in baseball. Across Double-A and Triple-A in 2025, Tong posted a 1.43 ERA, 0.92 WHIP, and 40.5% strikeout rate over 113 2/3 innings. Here is a breakdown of his Triple-A numbers.

Although Tong dominated the minors, he uncharacteristically struggled after being called up late last season. In 18 2/3 innings, he posted a 7.71 ERA, 4.96 xERA, and 1.77 WHIP. However, his 45.1% LOB rate and .396 BABIP against suggest he was unlucky in his first taste of big-league action.

For 2026, Tong will need a Mets starter to underperform or hit the injured list to earn a call-up. With Clay Holmes and Kodai Senga both showing inconsistency in recent seasons, that opportunity could arrive sooner than later. Right now, Tong is a fantasy stash in deeper leagues, especially if you can dedicate a roster spot and wait for his promotion.

Robert Gasser, SP, Milwaukee Brewers (1% rostered)

Level: Triple-A 

2026 Stats: 5.2 IP, 0.00 ERA, 0.88 WHIP, 47.8 K%, 13 BB%

Robert Gasser is not currently in the Brewers’ rotation, but that could change at any time. Both Brandon Woodruff and Kyle Harrison entered the season not fully healthy, and it’s still unclear what Brandon Sproat will provide. Plus, how many innings is Jacob Misiorowski going to pitch? Gasser is a left-handed pitcher who relies on command and pitch mix rather than overpowering velocity.

His fastball tops out around 94 mph, but he keeps hitters off balance with a sinker, slider, changeup, and cutter, with his slider being his best pitch against both lefties and righties. After undergoing Tommy John surgery in 2024, this is Gasser’s first full year back. In his first Triple-A outing of 2026, he dominated, striking out 11 batters over 5 2/3 innings while allowing only two hits.

Robert Gasser matches his career high by striking out 11 of 17 batters faced during a scoreless season debut at Triple-A 🔥@Brewers | @nashvillesounds pic.twitter.com/GEcbv43zmx

— MLB Pipeline (@MLBPipeline) March 28, 2026

Gasser has enough strikeout upside to warrant a stash in deeper fantasy leagues. If you don’t have the roster space to stash him, be ready to act quickly the moment he’s called up.

LIKE ROTOBALLER?

CLICK HERE, ENTER ROTOBALLER.COM, THEN CHECK THE BOX

More Fantasy Baseball Prospects and Rookies