These are the 10 hottest rookies over the past 30 days

August 9th, 2023

Welcome to the August installment of the MLB Pipeline Rookie Hot List. As we’ve done three other times this season, we’re taking a look at the top-performing rookies of each month.

As a sign of how much can change, seven players on this list did not appear in the July edition. In fact, two of them weren’t even in the Majors yet.

But before diving into the list, a quick reminder: this exercise does not look at who is most likely to come home with the Rookie of the Year Awards. That can serve as a tiebreaker, but we’re primarily looking at which rookies performed best over the past 30 days (using stats through Monday’s games).

Playing time is part of the consideration. Players like Freddy Fermin and Alec Burleson ran an OPS over 1.000, but their lack of plate appearances left them just shy of this list. Some relievers have been dominant as well, notably including Javier Assad, but didn’t pitch enough to measure up to the total impact of these 10 players.

Other honorable mentions include (in alphabetical order): Andrew Abbott, J.P. France, Gunnar Henderson and Matt Wallner. But now, without further ado, on to the list!

1. , 1B, Red Sox (previously unranked): Simply put, Casas has mashed recently. Among players with at least 75 plate appearances in the past month, his 217 wRC+ is second only to Freddie Freeman, and no other rookie is within 20 points of him. He has nearly half of his homers this season (eight of 17) in the last 30 days, which helped raise his slugging percentage from .398 to .475.

2. , CF, Dodgers (previously unranked): Outman's season has been a roller coaster, with a .415 wOBA through April before a .249 mark in May and June. But the 26-year-old has been on fire in the past month, slashing .361/.519/.525, with nearly as many walks (18) as strikeouts (19). Plus, solid defense in center field is a nice bonus.

3. , RHP, Guardians (previously unranked): Williams hasn't gone deep in many of starts -- he's gone beyond five innings once in his past five outings -- but they've all been terrific. He's given up to two or fewer runs each time, and he's held a K/9 above 10 in his past three starts, highlighted by a 12-strikeout, scoreless start on Sunday with just two baserunners allowed over seven innings.

4. , RHP, Mets (previous rank: 2): Senga continues to be one of the most consistent and durable pitchers in the league, let alone among rookies. And crucially, he's cutting down on two of his bigger issues compared to earlier in the season: walks (3.3 BB/9 vs. 4.7 BB/9) and home runs (0.3 HR/9 vs. 1.0 HR/9).

5. , SS, Reds (previous rank: 6): He may not have the name value of teammate Elly De La Cruz, but McLain has been the more consistent rookie -- and more productive lately as well. McLain leads all rookies with 25 hits in the last month, and he’s tapping into his power more. The 24-year-old has five homers in the last 30 days (92 PAs) after hitting seven homers in the first half (235 PAs).

6. , 2B, Twins (previously unranked): In the last 30 days, Julien is tied for second among rookies in hits (24) and third in walks (13), to give you an indication of his on-base prowess. Running a .477 BABIP in the second half is not sustainable, but his plate discipline numbers are looking much improved (0.62 BB/K vs. 0.32 BB/K).

7. , RF, Brewers (previously unranked): Frelick has been on a tear since his July 22 promotion. He's slashing .273/.435/.545 and tied for fifth among rookies in the last 30 days with 15 runs, despite only playing in 16 games. Don't expect him to hit so many home runs (three), but the plate discipline, speed, defense and on-base skills are here to stay.

8. , 2B, Athletics (previously unranked): Gelof has shown even more power in the Majors than in the hitter-friendly PCL, which is a pleasant surprise. He has five homers already in 20 games, which ties him for fourth among rookies and ties for fifth among all second basemen during that stretch. He could easily be slotted above Frelick.

9. , RHP, Angels (previously unranked): Silseth is perhaps the most surprising name on the list after spending the first half in relief or in the Minors. But he's been electric in his three second-half starts, with a 2.04 ERA over 17 2/3 innings and 26 strikeouts to just three walks. The only downside: all of the scoring came on four solo home runs.

10. , RHP, Guardians (previous rank: 4): Bibee was an inning away from all four of his outings the past month being quality starts. That's rare durability for a rookie. Homers continue to be a problem (four in 24 2/3 innings), but he's been able to limit the damage (2.55 ERA) by stranding a ton of runners (94.0 percent LOB rate).