Mel Stottlemyre Jr. thinks New York has affected Edwin Diaz

On a half-dozen occasions this season, Mel Stottlemyre Jr. has sat in the opposing dugout, watching his onetime protégé take the mound against his Marlins and perform to a variety of fates. Sometimes Edwin Diaz locked down a Mets win. Sometimes he didn’t.

Whatever the outcome, periodically Stottlemyre couldn’t help but think: This version of Diaz looks "very close" to the 2018 version when Diaz excelled under his tutelage in Seattle.

But with that, he had a theory. Maybe the bright lights of the Big Apple have negatively impacted Diaz.

"Man, I’ve seen that place tame a lot of people — and ruin some, too," Stottlemyre, the Marlins’ pitching coach, said during the Mets’ recent series in Miami. "It’s not a forgiving place to play. If you have a couple of hiccups in a row, you’re going to hear it from the fans and you’re going to see it in the headlines. And that’s pressure. Those are things that not everyone can learn to deal with.

"I can tell you probably deep down — he probably wouldn’t admit it — but I’m sure that had some effect on him."

Stottlemyre speaks through a lens of love, not criticism. He considers "Eddy" among "my all-time favorite players" from their three seasons together with the Mariners. Diaz, similarly, reveres Stottlemyre, who taught Diaz his signature slider grip during his first month in the majors, helping him transform from a reliever who threw exceptionally hard into a reliever who threw exceptionally hard and had a nasty second pitch. When the Mets and Marlins play, they make a point to catch up.

"You know the relationship that my dad had with Mariano?" Stottlemyre said. "I have that with him."

His dad, the late Mel Stottlemyre, is why he knows so much about performing in New York. The elder Stottlemyre spent more than three decades in the city as a pitcher for the Yankees and as a coach for the Mets and Yankees.

Since Diaz and Stottlemyre parted ways after 2018 — the pitcher traded to the Mets, the coach fired by Seattle and hired by Miami — Stottlemyre has had a frequent up-close view of Diaz’s struggles and triumphs.

"Pitching in New York is not easy. Seattle is a little different, a little more forgiving fan base," Stottlemyre said. "I don’t want to discredit anything he did. But Seattle is a much different atmosphere. And with that being said, there’s a lot less pressure."

Diaz’s Seattle finale was something to behold: A majors-leading 57 saves (in 61 tries), a 1.96 ERA, a 0.79 WHIP and more than 15 strikeouts per nine innings. He was so good that he received down-ballot Cy Young Award and even MVP votes despite being a reliever on a non-postseason team.

"It was the most incredible stretch that I’ve ever witnessed from a guy in the back end," Stottlemyre said. "Fun to watch."

That was the pitcher then-Mets general manager Brodie Van Wagenen sought in the Robinson Cano/Jarred Kelenic blockbuster trade that offseason. That is the pitcher the Mets have dreamed on ever since.

In three seasons with the Mets, Diaz has a 4.20 ERA and 17 blown saves (to 60 saves). At times, he has looked untouchable. At others, he has been maddeningly wild. The 2018 dominance has been elusive, including recently, when he failed to convert consecutive save chances.

Stottlemyre still sees the same Eddy Diaz.

"When guys get on a roll and they’re in a good spot with themselves, it leads to more aggressive pitches in the zone, confidence," he said. "Obviously, I know since he’s been over here he’s had some tough times and sometimes that will wear on you mentally. He looks like he’s in a good spot right now."