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Chris Clegg's dynasty fantasy baseball buy lows, sell highs, and MLB news for Week 21 (2025). Notable prospects debuts and dynasty risers/fallers including Samuel Basallo and Nolan McLean.
Welcome back, RotoBallers, to my dynasty fantasy baseball risers, fallers, and buys/sells for Week 21 of the 2025 MLB season. We are in the final stretch of the season. Whether you are in contention to win your dynasty league or out of it, there is still work to be done to improve your team for now and the long term.
Today's dynasty article will look at recent prospect call-ups like Samuel Basallo, Dylan Beavers, and Nolan McLean, along with several other dynasty-related news items. This bi-weekly series will examine various prospects and dynasty news and discuss fantasy implications. If you enjoy dynasty fantasy baseball, you know it is a fast-paced game. Keeping up with current events can help you stay ahead of your league mates.
Call-ups, trends, and buying and selling players are all just small pieces to help you stay ahead. So, that's what we will do in this article each week: break down everything you need to know to be successful in dynasty. At the end of the day, we all want to build a dynasty team that sustains and lasts for the long haul. I am here to help you do so. So, what do you need to know for dynasty leagues in Week 21 of the 2025 season? Let's dive in.
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Recent MLB Prospect Call-Ups
After dealing with some injuries and missing three weeks early in the season, Basallo is locked in. Basallo blasted 23 home runs in 321 Triple-A plate appearances while posting a .270/.377/.589 slash line. Reminder, he turned 21 years old just three days before his MLB debut, so it makes the performance even more impressive.
Basallo has a 108.5 mph 90th percentile exit velocity with a 116 mph max. His barrel rate was over 21 percent in Triple-A thanks to a 54 percent hard-hit rate and the absurd exit velocities he puts up on balls in the air. The average exit velocity of 94.1 mph is one of the best marks in all of baseball. On balls in the air, Basallo's exit velocities jump to 98 mph.
From a contact standpoint, Basallo’s 72 percent overall contact rate was around average for Triple-A, but age-adjusted is fine. The zone-contact rate trended upward all season and approached 85 percent by the time of his promotion. The chase rate and zone-swing rates were lower than you would like to see, but they are passable enough for Basallo to be a successful MLB hitter at a young age. Basallo should be added in nearly all formats right now.
We also got to see Beavers get the call and make his MLB debut, smoking a double in that game. Beavers hit 18 home runs in 418 Triple-A plate appearances, blowing past his career-best 15 that he hit in 531 plate appearances last season. The contact numbers have improved, and Beavers has seen his strikeout rate fall from 23.5 percent to 18 percent in 2025. The Triple-A slash line was impressive: .304/.420/.515.
A few small tweaks in the swing have unlocked a ton. It starts with a much smaller leg kick. Beavers is getting his foot down much earlier and is timing things up well. His hands are also in a slightly high position at the start of his swing. Last year, Beavers tipped the barrel a bit and had his hands slightly below his shoulders before the start of his swing. This year, his hands are a little above his shoulders before dropping the swing into the slot.
The Statcast data has steadily improved for Beavers throughout the course of the 2025 season. His average exit velocity of 88.5 mph has steadily risen all season, but the 105.4 90th-percentile exit velocity is close to plus. Being a selective hitter, Beavers picks his spots well and has great launch angles.
While Beavers is not the fastest runner, he has good reads and jumps on the basepaths. Expect Beavers to be a consistent 20 home run/20 stolen base type threat who will put up respectable batting averages and OBPs. He should play most days in Baltimore and is worth an add in all formats.
The Mets moved Frankie Montas to the bullpen and called up Nolan McLean for his MLB debut, and it was a good one. While he did walk four batters, McLean struck out eight across 5.1 scoreless innings against a very good Mariners lineup. Despite showing issues with control at times throughout the Minor League season, he has walked just 10.6 percent of batters. Since the start of July, the number has dropped, and McLean has struck out 33.3 percent of batters.
After being a two-way player at Oklahoma State, McLean got a chance to hit and pitch in pro ball. While the present power was there, the contact skills always held him back. McLean did not hit in a game after June 20, 2024, and focusing solely on pitching is paying off.
The numbers have been great this year as McLean has a 2.45 ERA with a 27 percent strikeout rate in 113.2 innings. In 18 of his 21 starts, McLean has allowed two earned runs or fewer. Walks have been an issue at times, but McLean does a good job of limiting the damage when he does put runners on base.
McLean’s fastball sits in the mid-90s with a heavy armside run. He throws from a 5’4” release height, which helps the pitch play at the top of the zone and has a rising effect despite the IVB not being overwhelming. With 10 or more inches of horizontal movement regularly, McLean has shown bat-missing ability with the offering.
The slider has around 10 mph of velocity separation from the fastball, sitting in the mid-80s with heavy sweeping action. It has late horizontal movement, which deceives hitters, largely due to its extremely high spin rates, which have been up to 3200 rpm. Watching the pitch, it is easily plus or better, and the metrics back it up.
McLean will mix a cutter and a curveball on occasion and has worked on a changeup. McLean has been using the cutter more often, and it worked at 91 mph last night. An upper-70s curveball has also been a nice addition to the arsenal. He will be sticking in the Mets rotation and should be added nearly everywhere for the upside he brings to the table.
Fantasy Baseball Dynasty Trends: Injured Players to Stash
At this point in the season, you have to ride hot streaks as long as they will take you, but there is also value in adding injured players to stash before they return. With six weeks left in the MLB season, some injured players won't contribute much of anything, especially pitchers who return later in September. The good news is, there could be some players that you could grab now to stash that could be of value.
Here is a list of MLB players to add for the stretch run of dynasty leagues.
| Player | Team | Position | Est Return |
| Shane Bieber | TOR | SP | ASAP |
| Kyle Bradish | BAL | SP | Next Week |
| Bryce Miller | SEA | SP | Next Week |
| Luis Garcia | HOU | SP | Next Week |
| Tylor Megill | NYM | SP | Next Week |
| Jac Caglianone | KC | OF | ASAP |
| Gabriel Moreno | ARI | C | Next Week |
| Adolis Garcia | TEX | OF | Next Week |
| Jacob Wilson | ATH | SS | End of Week |
Fantasy Baseball Dynasty Buys and Sells
Jakob Marsee is the hottest hitter in baseball. Is it legit? In 62 trips to the plate in a Marlins uniform, Marsee is up to four home runs, seven doubles, and a triple, while slashing .377/.468/.774. You could not have dreamed of a better start to Marsee's MLB career. This comes on the heels of an impressive Triple-A season in Jacksonville, where Marsee hit 14 home runs and stole 47 bases with a .246/.379/.438 slash.
Under the hood, Marsee is lighting up the savant page, and it is hard to nitpick anything. A 93 mph and a 14.3 percent barrel rate in a small sample are both impressive, and Marsee is smoking baseballs at ideal angles, having a 55 percent sweet spot rate. The contact is elite as well, with a zone contact rate of 91 percent and an 89 percent overall contact rate. Marsee has rarely expanded the zone with just an 11 percent chase rate.
It is interesting because Marsee had just an 85 mph average exit velocity in Triple-A with just a seven percent barrel rate. Yes, the contact rates were good in the minors, as were the chase rates, but it was just 78 percent overall contact in Triple-A. So what are the holes that could be exposed?
In Triple-A, Marsee had just a 68 percent contact rate on curveballs and sliders. While that's not a terrible number, it is possible we see Marsee begin to get exposed on more breaking balls against MLB pitchers. So if I had the chance, I would sell high on Marsee and try to get a top 100-150 dynasty asset from someone who really believes in the performance.
Michael Harris II is an easy buy for me. Through July 10, Harris had just a 44 wRC+ and a .205/.229/.310 slash line. He was legitimately one of the worst hitters in Major League Baseball. Harris implemented a swing change with his hands starting much higher and his stance much more open. It is working as Harris suddenly looks like one of the better hitters in baseball.
Since the swing change, Harris has a 197 wRC+ in 134 plate appearances with a .377/.391/.685 slash. He also has eight home runs and 21 extra-base hits. Given the mechanical change and data to back it, it feels like more than a hot streak. The average exit velocity over that span sits at 93.5 mph, and his barrel rate is up to 12 percent.
Sure, you can still poke a hole in his higher chase rate. That will always likely be part of his game, but when you make contact on 94 percent of swings on pitches in the zone, it is sure to play. I am buying Harris if possible and would be willing to pay a top 75 dynasty asset to get him, but it is possible you get him cheaper.
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