Why is Edwin Diaz a different pitcher in save vs. non-save situations for the Mets?

WASHINGTON — The greatest predictor of Edwin Diaz’s success in any given appearance this season has been not his strikeout rate or slider control or the weather or his catcher or the opponent or the amount of sleep he got the night before.

What has mattered is the score when he enters the game. Were the Mets winning by three runs or fewer?

Entering play this week, Diaz has a 0.50 ERA and 0.61 WHIP in 17 save situations, utterly dominant and every bit the closer former Mets general manager Brodie Van Wagenen thought he was getting.

But in 14 non-save situations — when the Mets were losing, tied or ahead by four or more runs — Diaz has been a bona fide liability, posting a 6.39 ERA and 1.66 WHIP.

Any idea why?

"Basically no. I just try to do my job," Diaz said on Monday at Nationals Park. "I got the same mentality when I come to save the game or come to a no-save situation. I’m just trying to do my job, get the outs."

Pitching coach Jeremy Hefner added: "I make nothing of that."

Those drastic splits might cost Diaz an All-Star appearance, too. His 2.92 ERA ranks 32nd among qualified National League relievers.

Fortunately for the Mets, Diaz’s save situations matter much more than the non-save situations. He has blown just one save all season, on June 1 against the Diamondbacks, and has been a big reason the Mets have been alone in first place in the NL East for seven weeks.

"I’m pretty happy about what I’m doing right now," Diaz said.

This is an extreme version of a problem Diaz has only dabbled with previously. In three seasons with the Mets, he has a 3.88 ERA in save spots, 4.18 ERA in other appearances. In his six-season career, those numbers are 2.70 and 3.94.

So this has not been a significant long-term hangup for Diaz. Hefner looks at it as pretty much a fluke over, so far, almost half of a season.

"If you don’t execute or you hit a guy and you walk a guy, you’re going to give up runs," Hefner said. "It just happens to be that they’re in non-save situations. I just don’t buy into it that much."

Some closers say that the adrenaline of a save situation — game on the line, nobody warming up in the bullpen, your team about to win or lose thanks to you — is such that it is hard to bring the same energy in a non-save situation.

Diaz said that "I feel the same every time." But Hefner allowed that perhaps the adrenaline factor is part of it for Diaz, while reiterating he doesn’t believe it matters too much either way.

"That could be something," Hefner said. "I don’t know. Relievers are funny. There’s a reason why they’re a reliever. They’re going to have execution problems at times. And problems isn’t the right word. Execution is going to come and go at times. And it may be that they’re not quite as locked in, they’re a little more erratic. Maybe you could tease that out. But he’s really good."

If Diaz is going to have a handful of bad outings, the Mets would rather they happen in non-save situations anyway.

"For sure," Hefner said. "Even in save situations, he’s not going to be perfect. He’s going to give up a run. And I know he hasn’t given up a home run and all this other stuff. But that’s not sustainable for any pitcher.

"He is elite. He has the stuff to go a whole year without giving up a home run, but we can’t expect that. So when it does happen, he’ll still be good. He’ll still be a really good pitcher."