Sean Gilmartin is a key piece of the Mets' bullpen

When the Mets selected Sean Gilmartin in the 2014 Rule 5 Draft, it was assumed that he would become the team's lefty specialist. Throughout the course of the season, though, the Mets brought in other pitchers to handle that duty. Despite these changes, Gilmartin has remained in the pen, becoming Terry Collins's only reliable left-handed reliever.

The Mets went through a series of lefties, with none of them claiming the role for good. Jerry Blevins got off to a promising start, but he suffered a serious injury in April, followed by a season-ending one in August. Alex Torres, known for his reverse platoon splits, was acquired in spring training, but his propensity to issue walks forced him to be designated for assignment. The Mets traded for Eric O'Flaherty in August, yet he's been unable to effectively get righties out. Through all of these failed experiments, the one lefty who remains is Sean Gilmartin.

In 49 innings pitched, Gilmartin is sporting a superb 2.76 ERA with a 2.59 FIP and a 8.9 K/9 ratio. Despite his supposed role as a lefty specialist, the California native is adept at retiring right-handed hitters, too–they've only managed a meager .239 wOBA against him all season, while lefties have mustered a paltry .293. Gilmartin has a penchant for ground balls–he coaxes them 47% of the time. His off-speed pitches, including his slow curve and changeup, make for weak contact, and he is one of the best on the team at generating weakly hit balls. This is the primary reason for Collins's confidence in Gilmartin in multiple-inning situations.

Between May 27 and July 17, Gilmartin went 13 consecutive appearances without allowing a run. In fact, he did not allow a single run in the month of June. The bullpen has had its peaks and valleys, but the 25-year-old has been steady all season, having never allowed more than two runs in any appearance.

A starter in the minors, the former Florida State Seminole's versatility is his greatest asset. In 16 of his 46 appearances, Gilmartin has pitched more than one inning. Notable outings include three brilliant innings in the 18-inning game in St. Louis on July 19 and 3.1 masterful innings in the record-setting win over Philadelphia on August 24. This is a common theme, though–Collins frequently uses Gilmartin in mop-up duty rather than in high-leverage situations. His reliability in long relief is excellent, but he should have no problem getting hitters out in close games as well.

The Mets are only 16-30 in games in which Gilmartin appears, but this has more to do with how Collins has used him. Gilmartin has been a stalwart in the Mets' bullpen, and he deserves a shot at pitching with the lead on a regular basis.