The Yankees may have summoned Justus Sheffield later than most September callups, but he also could have a bigger impact than most.
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The No. 27 prospect on MLB Pipeline's Top 100 and the top-rated prospect in New York's system, Sheffield gave up three unearned runs in one inning of work for Triple-A Scranton/Wilkes-Barre in the deciding game of the International League championship series on Saturday. After the RailRiders' season came to an end following that defeat, word leaked that the Yankees would promote the 22-year-old left-hander. He joined them on Tuesday.
Though Sheffield has been groomed as a starter throughout his pro career, New York shifted him to relief in late August in hopes that he could help them in that role during September and October. He logged a 2.91 ERA in seven bullpen appearances (four of them for multiple innings) down the stretch and during the postseason for Scranton.
With Albertin Chapman still on the disabled list with tendinitis in his left knee, Zach Britton and Stephen Tarpley are the lone lefties in the Yankees' bullpen as they try to hold off the Athletics for home-field advantage in the American League Wild Card Game. While Chapman is expected to return before then, the assumption is that Sheffield could pitch his way onto the playoff roster if he performs well in his first taste of the big leagues.

Sheffield certainly has the arsenal to do so. All three of his pitches earn at least plus grades when they're at their best: a mid-90s fastball with run and sink, a mid-80s slider and a mid-80s changeup. He should add velocity while pitching in shorter stints and his slider, which often is his top offering, should make him tough in left-on-left matchups.
A first-round pick (No. 31 overall) out of Tullahoma (Tenn.) High in 2014, Sheffield gave up a Vanderbilt scholarship to sign with the Indians for $1.6 million. Cleveland traded him and 2013 first-rounder Clint Frazier to the Yankees as part of a four-player package to land Andrew Miller in July 2016. Sheffield since has continued to blossom into one of the game's best lefty pitching prospects, with the upside of a No. 2 starter if he can further refine his control and command.
Despite being shorter than a typical starter at 6 feet, Sheffield creates downhill plane with his delivery and generates quality stuff without excessive effort. He's athletic and has been durable throughout his pro career with the exception of missing two months at the end of 2017 with a strained oblique.
Sheffield has enjoyed his best pro season in 2018, going a combined 7-6 with a 2.48 ERA in 25 games (20 starts) between Double-A and Triple-A. He had 123 strikeouts in 116 innings while limiting opponents to a .195 average, though he did issue 50 walks.
Regardless of what happens this fall, Sheffield should take on an even greater role with the Yankees next season. Luis Severino and Masahiro Tanaka are the only locks to return to New York's rotation and Sheffield has little left to prove in Triple-A.