Both Gsellman and Lugo came up in 2016 and helped pitch the Mets into the playoffs. Gsellman flashed a 95 MPH sinker which was nearly impossible to elevate while Lugo flashed a nasty curveball. In 2017, they took a step back performance wise as did their stuff. While both of them dealt with injuries, it’s also possible that their stuff plays better in the bullpen.
In a very small sample (four innings) as a reliever, Gsellman posted a 2.25 ERA and 1.91 FIP in his work in the bullpen. While in the bullpen, his sinker’s velocity averaged 94-96 whereas his sinker struggled to reach 93 as a starter. This is a common trend with pitchers who go to the bullpen. They gain velocity on their pitches which makes them tougher to hit. Starter turned reliever Brandon Morrow for example saw a three MPH jump on his fastball in just one season.
Even with his struggles in 2017, Gsellman had the 34th lowest exit velocity (out of 325) against him among pitchers with 150 balls in play against them. It’s possible his stuff plays better in the bullpen and he is able to generate even weaker contact.
Unlike Gsellman, Lugo’s 2017 was not a complete nightmare but it was definitely a step back from 2016. Despite his issues in 2017, Lugo held hitters to a .260/.299/.426 slash their first and second time through the order with a 3.26 ERA, 8.4 K/9, and 3.71 FIP. His third time through the order, hitters hit .352/.412/.506 with a .389 wOBA, and 4.91 FIP. Him in the bullpen makes perfect sense given the stark difference in his stats the first two times through the order and the third time through the order.
As for the stuff, Lugo’s fastball averaged 91 MPH in 2017. In 2016, he was around 91-93 as a starter but averaged more of 93-95 as a reliever. An uptick in his fastball as a reliever would go a long way to complement his curveball. His curveball generated the fourth (out of 422) highest spin rate in all of baseball in 2017 at 3,060 Revolutions per Minute.
Both have begun their transition to the bullpen this spring and have shown promising results. Lugo for example has a K/9 of 9.3 and Gsellman has three times as many ground ball outs to fly ball outs. Using these guys in a bullpen role as a “Relief Ace.” Many teams around baseball are doing this and it has worked very well for some, the Mets could be the next to reap rewards.