The Mets had the third highest bullpen ERA out of any major league team in 2018. In 2017, it was the second highest. While there were many reasons why those two teams were terrible, the abject awfulness of their relievers ranks high on the list. When Brodie Van Wagenen took the job as the Mets general manager, his number one priority was fixing a broken bullpen which had cost the team so many games over the past couple seasons.
Enter Edwin Diaz. The Mets surrendered an impressive package of talent to the Mariners in exchange for him and Robinson Cano—said package being highlighted by former first-round picks Jarred Kelenic and Justin Dunn—but based on the pitcher he had been the prior season, paying a high price was justified. The 24-year-old righty was arguably the single best reliever in all of baseball for Seattle in 2018, putting up a dominant 1.96 ERA/1.61 FIP with a league-leading 57 saves and a whopping 124 strikeouts in 73.1 innings. While Van Wagenen made other additions to the bullpen as well, Diaz was clearly the highlight, someone the Mets assumed would lock down the ninth inning not just in 2019, but for years to come.
It might be hard to remember in light of how his year ultimately went, but the season actually started out pretty well for Diaz. In his first 24 games, he more or less looked like the pitcher the Mets were expecting to get, as he put up a 1.64 ERA/2.76 FIP with 13 saves and 35 strikeouts in 22 innings pitched. Like any closer, he’d blown the occasional game—he suffered back-to-back losses in a series against the Reds, for instance, and his first blown save of the season came on May 25th against the Tigers—but the good far outweighed the bad up to that point. Between the discrepency between his ERA and his FIP and his unusually high HR/9 rate (after only giving up five homers in 2018, he’d already given up three on the season), there were perhaps warning signs for the troubles that were to follow, but the Mets nevertheless had plenty of reason to be confident in him at this time.
On May 29th, Diaz entered a game against the Dodgers in the bottom of the ninth with the Mets leading 8-5. By all accounts, it should have been an easy save even for a closer who was not of his caliber. Alas, things imploded for him very quickly, as he gave up back-to-back homers to start things off in the inning. Diaz subsequently gave up back-to-back doubles to make it four extra-base hits in a row, and just like that we had ourselves a tie ballgame. He was not able to record an out until three batters later, when he gave up a sacrifice fly with the bases loaded to give the Dodgers a stunning walkoff win. It was an embarassing performance for Diaz—just the second time in his career in which he gave up four runs in a game (interestingly, the first time he did it occurred exactly one year previously)—and it ballooned his ERA up from 1.64 to 3.22.
Still, it was only one game. There wasn’t necessarily any reason to believe that it was indicative of the kind of production (or lack thereof) we could expect to see from Diaz moving forward. And his next few appearances following his disastrous game against the Dodgers went off largely without incident. But then on June 13th against the Cardinals, he blew a two-run lead in the ninth inning. He subsequently came back out for the tenth inning and gave up yet another run to lose the game for the Mets. And then following that disappointing performance, he somehow had one which was even worse than the one against the Dodgers, as he gave up a whopping five runs on two homers in 0.1 innings to lose a game against the Phillies. And just like that, an ugly pattern was beginning to form.
Indeed, Diaz’s season kept on nosediving from there. He had another similar meltdown performance against the Phillies a few weeks later—as he once again gave up four runs while recording only one out to lose the game—but equally frustrating to those memorably awful performances were the long stretches in which he was unable to keep opposing teams off the board, even if it was only one or two runs he was giving up in these instances. He went one stretch towards the end of July and beginning of August, for instance, in which he gave up at least one run in five out of six appearances. And any time he would put together a small run of decent performances, he would subsequently go on another multi-game tailspin in which he gave up more runs and blew more games, making it impossible to ever gain any level of confidence in him.
The lack of consistency ultimately sank his season just as much as the handful of meltdown games did. Aside from April, he was unable to put up an ERA below 5.00 in any individual month in the season, and it was significantly higher than that most months. By the time August rolled around, he had effectively lost his closers job to the much more effective Seth Lugo, even though Mickey Callaway never formally announced that decision. Alas, that did not stop Diaz from blowing a few more games before the season was done—perhaps most noticeably in the nightmare game against the Nationals in which the Mets blew a six-run lead, with the last two runs coming against Diaz before he was able to even record an out. His final line on the season was predictably hideous: 2-7 with a 5.59 ERA/4.51 FIP, a 1.379 WHIP, 26 saves (and 7 blown saves), and 99 strikeouts over 58 innings pitched in 66 games.
In trying to dissect what went wrong for Diaz in 2019, there are a few obvious points. The long ball was a huge problem for him, as he gave up a staggering 15 homers for a HR/9 rate of 2.33. Some of that can be attributed to the juiced baseballs which gave so many other pitchers problems, but it can’t be used to wave away all of his struggles. Diaz’s control/command also became an issue this season, as his BB/9 rate jumped up from 2.09 in 2018 up to 3.41 and he often struggled mightily with pitch location, which allowed opposing hitters to tee off mistake pitches with relative ease.
That problem was perhaps most apparent with the use of his slider, which was his signature pitch in Seattle. It often remained incredibly impressive in terms of its sheer movement, but it was not quite as effective overall as it was previously. According to Brooks Baseball, for instance, the percentage of whiffs per swing Diaz induced with the pitch went down from 53.81% in 2018 to 43.22% this season, a rather stark decrease. Opposing hitters also did far more damage against the pitch than they had done previously. In fairness, the same could be said for his fastball, but not to quite the same extent as with his slider. Opposing hitters’ battting average against the pitch went up from .121 in 2018 all the way to .297 this season, and their ISO went up from .097 to a whopping .324. A lot of ink was spilled over his inability to throw the slider as effectively as he had in the past, and rediscovering the pitch’s former dominance will be hugely important if he wants to rebound from this season’s struggles.
But just how likely is such a rebound to occur? Moving forward, it’s difficult for the Mets to put too much faith in Diaz. He most certainly cannot be handed back the closers job, for instance, until he proves himself capable of excising the demons that haunted him in 2019. Having said that, the Mets are going to need to pray to the baseball gods that he will be able to do that if they want to finally overcome the bullpen woes that have held them back for three straight seasons. Regardless of how bad he was this year, the front office is unlikely to abandon him after giving up so much in exchange for him, especially considering the fact that he remains under contract for three more years. A bounceback season from him would provide a far greater addition to the relief corps than anybody the Mets could hope to bring in during the offseason, and it would go a long way towards helping the team improve in 2020.