There is BP and AP — before the pen and after the pen.

Steven Matz has been a different pitcher since his brief stint as a reliever before the All-Star break. In 16 starts, he had a 4.95 ERA and was 5-6 before his temporary stint in the bullpen. After, he has a 2.81 ERA and a 3-1 record in seven starts.

“It wasn’t like a, ‘Hey you better work on some things or you’re not going to start again.’ We knew he was going to be in the rotation again,” manager Mickey Callaway said after the Mets won for the third straight time, 9-2, over the Indians to start a nine-game homestand at Citi Field on Tuesday night. “But I’m sure a little bit of it might have helped him, getting a little bit of a break there.”

It sure seems like it.

Matz went 10 days between starts during his short stay as a reliever. He said he didn’t change much, but his results have improved. The left-hander turned in another quality outing Tuesday, holding the potent Indians to five hits and one earned run over 6 ¹/₃ innings, continuing his strong pitching since the All-Star break. The outing also followed a recent pattern of Matz shaking off his first-inning struggles that bedeviled him early in the year. He hasn’t allowed a first-inning run since the stay in the bullpen.

“You just learn from your mistakes early on,” Matz said. “It’s not anything crazy. Instead of trying to feel for what I have out there, it’s being a little more aggressive in the first inning, and that’s helped.”

He allowed a Jason Kipnis solo homer in the second and gave up an unearned run in the fourth. That was where he really turned it on. After a Todd Frazier error, the Indians strung together consecutive singles to pull even 2-2. But Matz retired Roberto Perez and Greg Allen and struck out opposing pitcher Shane Bieber looking. Of his seven strikeouts, six came without a swing, a sign of how good his stuff was.

“Some of those pitches were right there on the edge,” Matz said.

He retired the side in order the next two innings, and by then the Mets had the lead following Michael Conforto’s two-run homer in the sixth.

Unlike last week, when Callaway pulled a cruising Matz at 79 pitches in an eventual loss to the Braves, he stuck with the lefty Tuesday. Matz only got one out in the seventh, putting two runners on, before reliever Justin Wilson put out the fire by striking out Francisco Lindor and Oscar Mercado. But it was still another strong performance that all began with that brief demotion.