How should we view the performance of Edwin Diaz?

There’s not a Mets fan around who feels comfortable when Edwin Diaz comes into the game. It’s understandable, given that we just watched him give up 9 ER in a six-game span and that a three-batter save from him seems as common as a $2 bill. But are we being fair to him? Are our expectations for Diaz so completely out of whack that we can’t appreciate what he brings to the table?

Diaz’ 2018 was so good that the Mets vastly overpaid to get him. And then he was lousy in 2019. After a rough start in 2020, Diaz was very good in the Covid-shortened season. Now in 2021, Diaz has been mostly good, that one six-game stretch excepted. Almost every reliever goes thru a bad stretch. How good their year is depends upon both how long the bad stretch is and if there is more than one bad period.

Recently, we showed the results of the bad stretch with Jeurys Familia. Now let’s look at the 2021 leaders in Saves for another comparison:

Mark Melancon – 8 G, 7 ER in 7.1 IP
Liam Hendriks – 9 G, 5 ER in 9.1 IP
Alex Reyes – 5 G, 6 ER in 4 IP
Craig Kimbrel – No bad stretch yet
Matt Barnes – 11 G, 6 ER in 10.1 IP

Four of the five relievers with as many or more Saves this year as Diaz have gone thru brief stretches which saw their ERA be at least 2.5X higher than their overall ERA this year. Melancon has only given up 10 ER this season and seven of those came in his bad stretch. Half of Diaz’ 18 ER this season came in his recent six-game stumble.

In his first 32 games this year, Diaz had a 2.84 ERA, a 1.011 WHIP and held batters to a .532 OPS. Those are good numbers, with the WHIP and OPS suggesting that the ERA was a bit unlucky. His last five outings have been even better, with a 0.00 ERA, a 0.800 WHIP and a .410 OPS from opposing batters. Of course, those six games in between were pretty rotten. But, if Diaz avoids another bad streak like that, he’s going to end the year with strong overall numbers.

It’s tough to look at just one number when rating relief pitchers. If you just looked at his 3.80 ERA, you’d be missing the fact that Diaz has been fine for around 86% of the season to date. After having negative WPA numbers in his first two seasons with the Mets, Diaz has a 0.93 WPA so far this year. Of course, it pales in comparison to the 4.57 WPA he posted in 2018.

Among relievers, Diaz is third in the majors in +WPA, the positive value he brings to the table. He’s much lower than that in overall WPA because his negative value is so high. In his recent bad six-game stretch, Diaz had a 3.34 -WPA, which is both hard to do and really dragging down his overall value. Do those six games define his season?

The ERA is part of the story and can’t be swept under the rug. However, Diaz has a 2.12 FIP, which again suggests he’s been unlucky this season. He has a .356 BABIP – 34 points above his career mark – and a 64.9 LOB%, which is 12.7% worse than his lifetime results in the category. It’s tough to look good when both the hit gods and the sequencing gods are frowning in your direction.

As you all know, FIP looks to estimate a pitcher’s ERA by focusing on strikeouts, walks and home runs, the things most in control of the pitcher. Diaz has been great this year in limiting the gopher ball and his walks are down from a season ago, even if at a rate still higher than you’d like to see. He’s not matched his cartoon-like strikeout numbers from 2020 but a 13.3 K/9 is still a very nice number.

In 2020, Diaz had a 2.18 FIP and a 1.75 ERA
In 2021, he has a 2.12 FIP and a 3.80 ERA

Even with his recent six-game hiccup, Diaz is pitching just as well as he did a season ago, at least by FIP. But he has an ERA over two runs higher than last year. He was fortunate in 2020 and has been lacking in that department so far this season.

Let’s combine what Diaz has done in 2020 and 2021, both to enlarge the sample and, hopefully, to eliminate the luck. When we do that, we have 68. IP with a 3.03 ERA and a 1.215 WHIP. Diaz has a 2.14 FIP, so it’s not like fortune isn’t still playing a role in his numbers. But it’s nowhere near as extreme as his 2021 numbers alone.

Neither a 3.03 ERA nor a 1.215 WHIP are elite numbers for a reliever. But if we combine those two seasons for everyone and look at the top 10 pitchers in Saves – Diaz ranks ninth in this group – his ERA fits in comfortably with the back half of the sample instead of being the outlier he is this season in the category. Brad Hand (3.02 ERA), Kenley Jansen (3.06 ERA), Matt Barnes (3.00 ERA) and Raisel Iglesias (3.01 ERA) are in the exact same neighborhood.

We all want 2018 Diaz, both because that guy was great and we paid a lot to get that guy. But it seems pretty clear at this point that was a career year and it’s not really likely to happen again. Diaz was not good in 2019 but the past two seasons, he’s performed like a top-10 closer, at least in terms of Saves and ERA.

Most everyone was frustrated in the offseason when Hand was there for the taking and the Mets didn’t grab him after the Indians non-tendered him. Once he cleared waivers and became a free agent, Hand wasn’t going to come to the Mets because he wanted to be a closer and the Mets were committed to Diaz. But if you wanted Hand, shouldn’t you want Diaz, too? We’ve already seen how close their ERAs are over the past two seasons combined. Here are some other numbers in the same time frame:

Diaz: 68.1 IP, 29 Saves, 3.03 ERA, 1.215 WHIP, .603 OPS, 0.86 WPA
Hand: 65.2 IP, 37 Saves, 3.02 ERA, 1.036 WHIP, .603 OPS, 0.55 WPA

Not really much of a difference, is there? Let’s expand our sample, since we’re only about one season’s worth of innings here. Let’s include both 2019, when Diaz was bad, and 2018, when he was great, and see how the comparison to Hand holds up. For what it’s worth, Hand was a closer the entire time frame here, too.

Diaz: 199.2 IP, 112 Saves, 3.38 ERA, 1.107 WHIP, .629 OPS, 3.68 WPA
Hand: 195 IP, 103 Saves, 3.00 ERA, 1.123 WHIP, .651 OPS, 2.84 WPA

Again, not a whole lot to separate the two relievers here. Diaz holds a slight lead in four categories and has an edge in WPA while Hand has a better ERA. If given a choice, you’d pick Diaz but it’s not a slam dunk by any means. Overall, they’ve been pretty comparable over the past four seasons.

Maybe that’s the secret to understanding Diaz. Instead of expecting him to be the 2018 version of himself and considering him a failure when he doesn’t reach that standard, think of him as Hand – a top 10 closer. Think back to what the Mets had in 2018, before Diaz, when Familia and Robert Gsellman split the closer’s job. Did you consider them a top-10 closer? Before Familia, Jenrry Mejia was the Mets’ closer and he had a 95 ERA+ and a 1.484 WHIP. That’s not top-10 closer material, either.

It’s a very defensible position to believe that the closer is overrated in 21st Century baseball. It’s also fair to consider all of the blown saves in games started by Jacob deGrom in 2017-18 and be a proponent of having a top-notch closer. Diaz hasn’t been an elite reliever since joining the Mets but he’s been a top-10 closer the past two seasons. It may not be what we expected – or paid for – but it’s still a good thing to have on your club.