Breaking down the recent flurry of top prospect promotions -- and who's next

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The Minor League season may be winding down to a close, but prospect transactions sure haven’t, as you may have noticed in recent days.

Since last Thursday alone, three Top 100 prospects have been promoted and made their Major League debuts -- in order of first game: Cubs outfielder Owen Caissie, Mets right-hander Nolan McLean and Orioles catcher/first baseman Samuel Basallo. Is this a coincidence? Not at all, at least in the case of the last two.

Players called up Aug. 15 or later won’t exceed 45 days of Major League service time this season, which ends on Sept. 28. That is to say, they won’t graduate from prospect status unless they also exceed 130 at-bats or 50 innings pitched first. (As it stands, Caissie would graduate on days on Sept. 28 exactly.) By calling them up now, clubs preserve that rookie eligibility for 2026 while giving their young talents Major League experience they can learn from for next year and beyond.

Rookie eligibility is important because prospects who appear on two of three preseason Top 100 prospect lists (MLB Pipeline, Baseball America, ESPN) are eligible to win their organization a Prospect Promotion Incentive pick if they a) are up in the bigs within two weeks of the start of the season b) win Rookie of the Year or c) finish top three in MVP or Cy Young before becoming arbitration-eligible. More on PPI eligibility here.

But such exciting moves aren’t exclusive to the Majors this time of year.

There are only three weeks left on the calendar for Single-A and High-A, four for Double-A and five for Triple-A. If you’re a team that wants to get its best prospects some well-earned promotions and experience at tougher levels before the long, cold winter, now is the time to make those transactions. We’ve already seen that with players like Jesús Made (High-A), Colt Emerson (Double-A) and Travis Bazzana (Triple-A) moving up already this month. Then, news broke Sunday night that Konnor Griffin and Leo De Vries -- two of the top three prospects in the sport -- are both headed to Double-A this week.

With so much movement going on -- and potentially more still to come -- let’s look at what recent transactions mean for three Top 10 overall prospects and which others in that stratosphere could follow in their footsteps:

Konnor Griffin, SS/OF, Pirates (No. 1): The 2024 ninth overall pick’s trademark power and speed have been on full display in his first full season as he sits with 16 homers and 59 steals through 101 games at Single-A and High-A. But most notably, his hit tool has been even better than advertised, leading to a .332 average, .414 OBP and 21.3 percent strikeout rate before his ascent to the upper Minors. A right-handed hitter, Griffin has streamlined his load, making him more direct to the ball and helping drive that solid contact rate.

But those adjustments will be challenged with his move to Altoona. Griffin looked especially susceptible to pitches down and away at High-A Greensboro, and you can bet more experienced Double-A arms will attack him consistently there. At worst, early Eastern League speed bumps could give Griffin a primary focus ahead of a return there for 2026. At best, he could keep his momentum going and put Pittsburgh even more in his sights for next summer.

Leo De Vries, SS, Athletics (No. 3): This year’s biggest prospect acquisition at the Trade Deadline, De Vries certainly ended his brief stint with High-A Lansing on a high note, going 7-for-12 (.583) with two homers, two triples and a double in his final three games. Incorporating his time with Fort Wayne in the Padres system, the switch-hitting shortstop is one of only nine players aged 18 or younger to receive 350 plate appearances at High-A in a single season since 2006; among those nine, only Sebastian Walcott (124, 2024) has posted a higher wRC+ than De Vries’ 118.

So no, it doesn’t come as a huge shock that a player who has been pushed aggressively since signing for $4.2 million in January 2024 has received another big assignment.

Unlike Griffin, De Vries hasn’t enjoyed end-to-end consistency in 2025, especially when it comes to his hitting from the right side. His performance in Double-A will need to be graded on an even bigger curve, considering he’ll be the youngest player at the level this season. Also of note, he joins a Midland team that also has 2024 third-rounder Joshua Kuroda-Grauer. Neither player has played somewhere other than shortstop in ‘25, so something will have to give.

Samuel Basallo, C/1B, Orioles (No. 8): Jonathan Mayo already thoroughly covered what to expect from Basallo in the Majors. Make sure you click through to see just how many spots the 21-year-old backstop occupied on Triple-A statistical and analytical leaderboards.

The truth is right there that Basallo has been a Major League-quality hitter for some time now, but his defensive fit remained up in the air long enough to hold him back in Triple-A Norfolk. As Jake Rill notes, the Orioles plan to rotate Basallo through catcher, first base and DH to get their latest phenom as much exposure to MLB pitching as possible, thus kicking the full-time fielding questions down the road a bit further.

Who could be next?

Kevin McGonigle, SS, Tigers (No. 2): This could be aggressive since McGonigle has only played 26 Double-A games. However, he played only 50 for High-A West Michigan (dating back to 2024) before getting his latest promotion, and he hasn’t lost a step at the Minors’ second-highest level, hitting .286/.390/.582 with 15 extra-base hits, 18 walks and only 12 strikeouts. It’s certainly possible Detroit prefers to keep McGonigle with a loaded group in Erie, which already has an Eastern League postseason berth, but if it wants to challenge him before September is out, there’s only one MiLB stop left: Triple-A Toledo.

JJ Wetherholt, INF, Cardinals (No. 6): St. Louis president of baseball operations John Mozeliak suggested last week on 101 ESPN that the 2024 seventh overall pick may not get a late-season callup because he isn’t entering Rule 5 eligibility this offseason and doesn’t need the 40-man spot just yet. But Wetherholt is certainly pushing the issue at Triple-A. His nine homers with Memphis already trump his total of seven in 36 more games at Double-A Springfield. His .670 slugging percentage and 1.073 OPS rank third and fourth, respectively, at Triple-A since his debut on July 9. By the end of the month, the left-handed slugger could force the Cards to see what they have in him in The Show before they make other offseason decisions.

Bubba Chandler, RHP, Pirates (No. 7)/Andrew Painter, RHP, Phillies (No. 10): Both seemed like they would have already been up in the Majors before this, but Triple-A inconsistency by both has kept that call from being a reality to this point. That said, the Pirates just moved Andrew Heaney to the bullpen and could give Chandler a late look for the exposure as much as anything, and the Phillies, currently down a starter due to Zack Wheeler’s issues with a blood clot in his right upper body, should have an all-hands-on-deck approach as they try to hold off the Mets in the NL East.