For left-handed reliever Chasen Shreve, the last few years have been a rollercoaster. After being drafted by the Atlanta Braves in the 11th round of the 2010 draft, Shreve made his debut in 2014, with a 0.73 ERA in 15 appearances out of the Braves' bullpen. He was promptly shipped to the Yankees for former standout prospect Manny Banuelos, and wasn't even considered to be the major part of the deal. Reliever David Carpenter was supposed to join Dellin Betances and Andrew Miller to form a bullpen that was comparable to the Royals.
Instead, Carpenter's effectiveness inexplicably fell off a cliff, while Shreve essentially did what Carpenter was supposed to do. From the start of the 2015 season to the end of August 2015, Shreve threw 52.1 innings in 49 appearances, with an ERA of 1.89. Behind a low 90's fastball and a lethal changeup with splitter-like movement, Shreve amassed just under 10 K/9 during the 2015 season.
After August, he appeared to implode out of nowhere. He made ten appearances, only tallying six innings with a 13.50 ERA. His sudden ineffectiveness carried into the 2016 season, as he had a 5.18 ERA in 33 innings over 37 appearances, also spending time in Triple-A Scranton. At 26 years of age, Shreve will need to regain his stuff quickly, or his time in the Bronx might be limited.
Even during his glory days of April to August 2015, Shreve's peripheral stats suggested that he was incapable of sustaining such an impressive level of dominance. During that time period, he had a 3.86 FIP, with over four BB/9. Specifically, he had a left-on-base percentage (LOB%) of 92.9%, which is well above the league average. The general belief is that stats like a pitcher's LOB% will regress back to the league average over a sufficient amount of innings.
Despite still generating a large amount of swinging strikes, Shreve's changeup has also come down to earth. In 2015, opposing hitters had a .464 OPS against his offspeed pitch, compared to a .752 OPS this season. As nasty as his changeup is, his woes seem to be concentrated around his fastball, which yielded a .906 OPS in 2016.
In early 2015, Shreve would pound the bottom of the strike zone with his fastball. Here is how he located his fastball until the end of August 2015:
Since then, he has lost his command, leaving his fastball in the middle of the strike zone more often:
Spotting his fastball at the bottom of the strike zone may have complimented his changeup, which he tries to bury below the strike zone. Keeping everything in the same general vicinity must have gone a long way in generating deception and keeping hitters off balance. However, since September of last year, he hasn't been able to locate his fastball as effectively, and both of his most commonly used pitches have suffered. Whether the two are related is unclear, and his peripheral stats always suggested that he was more of a middle reliever anyway. After looking at his 2016 numbers, lowering the location of his fastball is definitely worth a try.
Data and charts are courtesy of FanGraphs.