Normally, I secretly enjoy the September roster expansion in baseball. I understand the criticisms of suddenly letting teams have up to 40 players rather than 25. I know it's weird that teams are playing with different sized rosters, that the various levels of quality can swing playoff races, and that sometimes the games themselves more closely resemble the All Star Game than what we've typically seen over the last 5 months.
But I still really have enjoyed September because we get to see more players, we get a preview of seasons to come with dynamic young players, and because it provides actual strategic options for managers to pinch hit or use their bullpen differently after a season of rigid usage patterns and three-man benches that discourage pinch hitting. It more resembles the strategic game that I love more than the less dynamic game it has become. In the last couple of years, baseball has become more checkers than chess, and it's nice that it can become chess again for at least one month.
But, of course, this year the September callup crop figures to be fairly depleted. All year, teams have been aggressive in promoting rookies into prominent roles on their Major League rosters. Of the prospects on Baseball Prospectus's top 101 list at the start of the year, 13 of the top 20 (Byron Buxton, Addison Russell, Carlos Correa, Francisco Lindor, Kris Bryant, and Noah Syndergaard, Archie Bradley, Miguel Sano, Jonathan Gray, Joey Gallo, Blake Swihart, Joc Pederson, and Jorge Soler) have spent significant time in the Majors. Alex Meyer also had a brief cup of coffee as well.
So there won't be nearly as many impact players coming up as there would normally. However, here are a few of the guys who could have a serious impact on the rest of the season:
Javier Baez, Chicago Cubs
Baez struggled mightily last year when he was a consensus Top 10 prospect, striking out in 94 of his 229 plate appearances as a 21 year old in the Majors, and was somehow even worse during Spring Training. So the Cubs left him in Des Moines all season while primarily relying on Russell and Starlin Castro. Baez hit .324/.384/.527 with 13 homers in 313 plate appearances, and stole 17 bases in 20 attempts. While he walked 21 times and struck out 76 in 328 plate apearances, that's actually a big improvement over his 2014. Baez has dynamic bat speed and raw power and fields well enough to hold down a spot in the middle infield if given the opportunity. If only he can get his strikeouts under control, he could supplant Castro and be a huge contributor to the Cubs in the postseason.
Kennys Vargas, Minnesota Twins
Unlike Baez, Vargas made a significant impression in 2014 when he hit .274/.316/.456 in 234 plate appearances for the Twins. A giant young hitter with prodigious power, Vargas was similar to Baez in that he could not control the strike zone, however. A disappointing April and May (.245/.277/.365) led to his demotion to double A, where he raked his way back through the minors (.283/.414/.496 combined). If he can harness the strike zone in the Majors, Vargas can be an asset to a Twins team that's still in the playoff hunt, allowing the Twins to rest the replacement-level Joe Mauer against lefties and as a big threat off of the bench.
Dalton Pompey, Toronto Blue Jays
The Jays are still battling with the Yankees for control of the AL East, and Pompey might be someone who can help them. He struggled out of the gate after breaking camp with Toronto, hitting .193/.264/.337 in 91 plate appearances. His struggles continued when he was sent down to Triple A, and he was demoted again to Double A New Hampshire in early June. But he hit .351/.405/.545 there to earn his way back to Buffalo, where he hit .327/.414/.414. Pompey doesn't figure to hit for much power, but is a strong defensive player and capable baserunner who could steal some time away from Kevin Pillar, especially versus right handed pitchers.
Dario Alvarez, New York Mets
The Mets have, against all expectations, put together a tremendous season in spite of a lot of hardship. They have eight players currently on the 60 day DL and have lost Travis d'Aarnaud, David Wright, Lucas Duda, and Stephen Matz for extended periods. One area where they haven't been able to come up with an answer is in the bullpen, specifically left-handed relief help. Alvarez would be ideally suited to help there, being left-handed and all. He also has struck out 60 batters in 41.1 innings across double and triple A, including 17 in 10.1 innings at Las Vegas. Better still, lefties have hit just .125/.241/.181 off the 26 year old. If the Mets install him in their bullpen, he should easily supplant Eric O'Flaherty as their primary LOOGY with an option to become even more.
Julio Urias, Los Angeles Dodgers
Don Mattingly has gone on record saying that the 19 year old Urias, a consensus top 10 prospect, will not be on the Dodgers' roster for all of September, but that he might get a call later in the month to pitch out of the bullpen. Urias is still almost indescribably young, but struck out 74 batters while walking only 15 in 68.1 innings at Double A. The Dodgers have to be cautious with such a young and valuable arm, but it has to be so tempting for Andrew Friedman to think about using him like he did David Price in 2008 or Matt Moore in 2011 in Tampa.
Jameson Taillon, Pittsburgh Pirates
Speaking of which, there's Jameson Taillon. Taillon has been incredibly snakebit over the last couple years, requiring Tommy John surgery in 2014 and then requiring surgery for a hernia just as he was about to start rehab. He should be off of the DL at some point in September, at which point the Pirates can decide if they want to throw the 21 year old prospect into the fire as a potential option out of their bullpen. That would be a huge step for the youngster, and maybe too aggressive, but the notion of a 6'5" youngster pumping 97-98 mph fastballs in the playoffs might just be too seductive to pass up.