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Three top fantasy baseball prospects - Jacob Misiorowski, Andrew Painter, Marcelo Mayer - that can make big impacts. These MLB prospects are waiver wire pickups or stashes.
With Memorial Day behind us, we've reached the heart of the fantasy baseball season when roster management is critical to setting yourself up for the stretch run. If your team needs a boost, some excellent young prospects are on the way with plenty to offer for their MLB teams and your fantasy team.
Three of the big-time prospects on the radar right now are Jacob Misiorowski of the Milwaukee Brewers, Andrew Painter of the Philadelphia Phillies, and Marcelo Mayer of the Boston Red Sox. In this article, we will examine the fantasy upside of each prospect and whether it makes sense to add any of them to your roster at this point in the season. Depending on your league size, roster construction, and current standings, each player can be a great pickup in the right spot.
Let's examine the circumstances for each of these three prospects and determine where they should be stashed or grabbed off the waiver wire before it's too late.
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Jacob Misiorowski, SP, Milwaukee Brewers
Current Level: Nashville Sounds (Triple-A)
Availability: 8% rostered
2025 AAA stats: 11 G, 3-1, 1.60 ERA, 3.14 FIP, 71 Ks, 22 BBs, 56 1/3 IP
Misiorowski has been extremely impressive in Triple-A this season, and his high strikeout numbers could make him an instant fantasy star when he gets the promotion to the majors. The 23-year-old righty was ranked as the No. 2 in the Brewers' farm system by Fangraphs and the No. 4 prospect in the system by MLB Pipeline.
The Brewers drafted him in Round 2 of the 2022 MLB Draft, and the 6-foot-7 athlete features a fastball that frequently gets to 100 miles per hour and some plus-plus sliders. In 2024, he split time between Double-A and Triple-A, compiling a 3-5 record and 3.33 ERA but also posting an impressive 127 strikeouts in 97 1/3 innings.
This year, he went back to Triple-A and has been outstanding. His strikeout rate has stayed above 11 K/9, and lately he has been almost unhittable.
Jacob Misiorowski is on an epic heater.
He has a 0.96 ERA and 50 strikeouts over his last 37.2 Triple-A innings 🔥🔥
(🎥 @BrewersPD)
— Baseball America (@BaseballAmerica) May 27, 2025
Misiorowski was expected to arrive mid-season as a Josh Hader-type option out of the bullpen, but he has been so good as a starting pitcher that the Brewers may look to move him up into the MLB rotation instead.
Right now, though, the Brewers don't have any room in the rotation. They just sent promising prospect Logan Henderson back to the minors since Brandon Woodruff and Jose Quintana are close to returning. Freddy Peralta, Chad Patrick, Aaron Civale, and Quinn Priester are currently in the rotation, with DL Hall also in the mix.
Henderson and Misiorowski both look ready to produce effectively at the major league level, but they are currently without a slot in the rotation. However, as the summer goes on, the Brewers will likely give both youngsters a chance. Either or both could work out of the bullpen or replace a veteran option who gets hurt or struggles. Whenever Misioroski receives the call, he'll be a great addition in all formats with his strikeout upside. He brings enough punchout potential that he could even be worth a look if he's pitching out of the bullpen.
Stashing Misiorowski is a strong option in NL-only leagues, but he's hard to hold in standard mixed leagues since there isn't a clear path to playing time for him right now. Get ready to jump on him, though, as soon as that changes. The same goes for Henderson, who was very effective in his audition but still ended up back in Triple-A.
Andrew Painter, SP, Philadelphia Phillies
Level: Lehigh Valley Iron Pigs (Triple-A)
Availability: 16% rostered
2025 minor league stats: 7 G, 1-2, 3.09 ERA, 3.92 FIP, 27 Ks, 17 BB, 23 1/3 IP
Painter is the top prospect in the Phillies' system and one of baseball's top pitching prospects. According to MLB Pipeline, he is the No. 5 prospect in baseball and the second-best pitching prospect behind only the Pirates' Bubba Chandler. Painter has reached Triple-A after starting the season in the low minors and is just one stop away from joining the MLB rotation.
The Phillies added Painter with the No. 13 pick of the 2021 MLB Draft out of Calvary Christian Academy (high school). The big righty has posted impressive numbers at every level and looked to be ticketed for a fast rise to the majors before missing both 2023 and 2024 following Tommy John surgery and his recovery.
He didn't return to the field until last fall, when he earned the Arizona Fall League’s Pitcher of the Year Award. He only pitched 15 2/3 innings in the AFL, but had an impressive 2.30 ERA, a 0.89 WHIP, and a .189 batting average while stacking up 18 strikeouts.
He dominated in Single-A while building up his pitch count and moved to Triple-A for his three most recent starts. He gave up three runs in those three games with 15 strikeouts in 12 innings. He allowed nine hits and issued six walks in those outings and continues to ramp up his pitch count slowly.
In his next start on Wednesday, he is expected to get up to 80 to 85 pitches.
Andrew Painter will pitch Wednesday and he’ll throw either 6 innings or 80-85 pitches, per Rob Thomson.
Asked Thomson how many more starts the #Phillies expect Painter in Triple-A.
He still said July was the target. That’s at least 4 more.
— Jeff Kerr (@JeffKerrCBS) May 27, 2025
He has had some control issues in Triple-A and hasn't been quite as lights out as in other stops, but he still has a few starts to work through those issues before he moves to Philly. Based on what we have seen from Painter, he has the potential to make a huge impact when he arrives in Philadelphia. He is still on track for a July arrival, and since he's only 22 years old, the Phillies can still afford to take their time to move him to the majors.
After the All-Star break, Painter could make a few exciting showcase starts, but it remains to be seen how many innings he can pitch down the stretch and possibly into the playoffs. He has a high enough ceiling to be worth stashing if possible, even though he is still over a month away.
Whether he's worth the wait depends on your league settings and roster construction. When he arrives, he'll be a great option and have the potential to make a huge impact for the Phillies and your fantasy baseball squad as he joins a top-flight team with an already-stacked rotation.
If you play the waiting game with Painter, try to be the manager who takes the plunge early enough to have him for his arrival in July.
Marcelo Mayer, IF, Boston Red Sox
Current Level: Boston Red Sox
Availability: 26% rostered
2025 AAA stats: 43 G, .271/.347/.471, 9 HRs, 43 RBI, 31 R, 2 SB
2024 MLB stats: 3 G, .250/.250/.333, 2B, R, 3 Ks
The Red Sox continue tapping into their talented farm system, adding rookie Marcelo Mayer to the infield mix and rookie Kristian Campbell. Mayer started the year in Triple-A after an impressive spring training and got the call to the majors when Alex Bregman (quad) went down due to injury.
Mayer was hitting .271 with a .363 wOBA and nine homers in his 43 games at Triple-A. His nine homers were more than he hit in all of last year, and he was also on pace for a career high in RBI since he had 43 RBI in 43 games, repeatedly coming up big in the clutch.
Since arriving in the majors, he has gone 3-for-12 (.25) with a double and a 44.4% hard-hit rate.
Marcelo Mayer staying hot! pic.twitter.com/jtXTgz6vbK
— Tyler Milliken (@tylermilliken_) May 26, 2025
According to MLB Pipeline, Mayer was the No. 8 prospect in baseball. He has a well-rounded skill set as a classic "five-tool" prospect. He has consistently made effortless contact and is now adding more power as he continues to develop. He has good speed but has only attempted two stolen bases in Triple-A and was successful in both attempts.
While he doesn't have one elite skill, he has a well-rounded game and good plate approach. He should be able to contribute across the board as long as he's in the mix in the Red Sox infield. He has worked at shortstop most of his time in the minors, but also played both 2B and 3B. With Bregman out, the Red Sox could continue to have Mayer fill in at 3B and 2B or move Trevor Story to one of those spots.
Mayer may not have a long-term spot secured, but if he plays well, the Red Sox will make room for him since he's a huge piece of their future. His versatility should also help him fill multiple infield spots for fantasy baseball. The team wouldn't have called him up to sit on the bench, so he should be in an almost everyday role going forward.
In standard mixed leagues, Mayer is a solid pickup, although he doesn’t have elite power or speed, so you don’t have to break the bank to add him. If you need solid production from an infield spot, though, Mayer is definitely worth a look. In dynasty or AL-only leagues, Mayer has even more value and is worth rostering in most formats.
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