The Mets’ second-half relief corps is the tale of two bullpens

The Mets are soaring through the standings with a 21-7 record in the second half—the best in baseball—on the backs of solid offense and superlative starting pitching. But the bullpen, while far from the unmitigated disaster that seemingly sunk the team in the first half, has not reached the same heights, and there’s a growing divide between the relievers who have helped lock down wins during this stretch and those who have hindered it.

The Good

Any conversation about the brights spots in the Mets bullpen starts and ends with Seth Lugo. The MLB Reliever of the Month in July has not slowed down in August, and he now sits on a 0.61 ERA in the second half across 12 appearances. His strikeout rate is well over 11 batters per nine innings, matching his season rate, and he is generating grounders on a whopping 62% of balls put in play against him—an immensely valuable trait in this home run era. It’s no surprise that he’s expected to get more save opportunities, and frankly it couldn’t have come soon enough.

Luckily for the Mets, and for Lugo’s arm health, he’s not alone in providing solid relief outings in the second half. Lefties Justin Wilson and Luis Avilan have combined to allow just two earned runs in 21 innings over that span, and while both are walking batters at a higher rate than you’d like to see, they are generating a lot of strikeouts and ground balls and keeping runs off the board. As expected, both are best against left-handed batters—but not to the point that they are a serious liability against a righty or two.

The Bad

If Lugo is the essence of what is working with the Mets bullpen right now, Edwin Diaz is his inverse. He may not have the worst outcomes among all Mets relievers, but the gap between his production and what the Mets expected and needed from him is simply cavernous. His second-half ERA is nearly 6, but his FIP is even higher, buoyed by four home runs, the most allowed by any Mets reliever in the second half. There are still glimpses of the enormous underlying talent, as he’s striking out more than a third of the batters he faces, but he remains a major obstacle as the Mets try to field a stronger bullpen through this playoff race.

Diaz is not alone in his struggles in the back end of the bullpen, as Jeurys Familia and Robert Gsellman are displaying huge red flags during almost every appearance. Both sport ERAs under 4 for the second half, but they disguise some major concerns for the Mets going forward. Familia is walking nearly a batter an inning, even more than he was walking during his early season struggles. And while he’s still a ground ball pitcher, the quality of contact against him is quite good and it’s only a matter of time before his 89% strand rate drops and the runs start to score. On the upside, his outing on Sunday was downright dominant.

Like Familia, Gsellman’s second half ERA belies an underlying worry, but in his case, it’s a plummeting strikeout rate and a spike in home runs. He’s struggling to get swings and misses, and while his velocity hasn’t been noticeably affected yet, it’s reasonable to consider whether his significant workload—the fourth-most innings among all relievers on the season—is starting to wear him down. What’s certain is that he doesn’t have the profile to keep up the .245 batting average on balls in play that is covering up a number of warts, and the Mets need to figure out how to get him more rest before the impending implosion hits.

The Verdict

With a lot of season left to play, it’s clear that while the bullpen has made a huge turnaround in the second half in terms of results, as their collective second half ERA is two full runs lower than their mark in the first half. But there’s a lot of cause for concern in terms of peripherals—strikeouts, walks, and home runs—that have barely budged at all.

Some new faces offer promise, particularly Brad Brach, added recently after he was designated for assignment by the Cubs. Donnie Hart, another recent waiver claim, was optioned to Triple-A for Brach, but both potential and have been less heavily worked than some season-long Mets. The minor league depth continues to be worrisomely thin, and the team should seriously consider adding more arms from the the pool of any forthcoming DFAs to increase the odds that someone will stick. The bullpen nearly sunk the team in the first half, and despite improvements, they still very much have the capacity to do it again in the second.