Mets pinch-hitter Wilmer Flores is mobbed at home plate by...

Mets pinch-hitter Wilmer Flores is mobbed at home plate by teammates after his walk-off home run against the Phillies during the 10th inning in Game 1 of a doubleheader at Citi Field on Monday. Credit: Mets pinch-hitter Wilmer Flores is mobbed at home plate by teammates after his walk-off home run against the Phillies during the 10th inning in Game 1 of a doubleheader at Citi Field on Monday.

Wilmer Flores is the Mets’ walk-off king.

Flores blasted a pinch-hit home run in the bottom of the 10th inning to give the Mets a 4-3 win over the Phillies in the opener of the teams’ doubleheader Monday at Citi Field.

Philadelphia took the nightcap, 3-1, as Flores’ RBI double in the ninth saved the Mets from being shut out for the third time in four games.

The walk-off hit in Game 1 was the 10th of Flores’ career, passing David Wright for most in franchise history — in considerably less playing time. Wright’s nine game-end ers came in 6,869 plate appearances. Flores — rarely more than a utility infielder or a fill-in starter for injured teammates — passed Wright in plate appearance No. 1,790.

“It’s almost getting to the point where you expect it,” Zack Wheeler said. “When the game is on the line, that’s the guy you want to have up there.”

Said Flores: “I’ll tell you that this time I was thinking about a walk-off, because I know everybody [else] was.”

The Mets have five walk-off wins this year, matching their 2017 total. Flores has accounted for four of them and has four walk-off homers in his career. In the latter category, he is tied for most in Mets history with Mike Piazza, Cleon Jones, Kevin McReynolds and Chris Jones.

This one came with an assist from the umpiring crew. On a 2-and-1 count, Phillies righty Victor Arano came up and in with a fastball that appeared to catch Flores’ right forearm. It was called a ball, and after the Mets challenged, the call stood.

Said Wheeler: “It did hit him. We saw it on the replay. I’m glad they didn’t overturn it.”

Arano’s next pitch was another fastball, this one on the inner half of the plate. Flores turned on it, ringing it off the leftfield foul pole. That lifted his average to .300 and OPS to .868 since May 4. “It doesn’t get old,” he said.

“You know, some guys just step up in those situations,” manager Mickey Callaway said. “I guess he’s been very successful in the past about it.”

Wheeler lasted 4 2⁄3 innings, his shortest start since May 16, and allowed three runs.

The Phillies scored in the first (Nick Williams’ RBI single) and the second (Rhys Hoskins’ RBI single) and then erased the Mets’ 3-2 lead on Maikel Franco’s solo homer to left-center in the fourth.

After Wheeler scattered seven hits, walked three and struck out eight, Callaway pulled him at 102 pitches in favor of Seth Lugo. Wheeler wanted more.

“I was pretty mad when I came out because I wanted to get to the sixth inning,” he said. “I was finally feeling good. Earlier on, I didn’t have a good feel for the ball and I started to get that the deeper I got. I was kind of upset, but not my call.”

Said Callaway: “A lot of pitches in his outing today. We wanted to get a fresh arm in there with runners in scoring position. But he really battled. When you have games like that and you battle and you keep us in it, you do your job. And I thought he did his job today.”

Lugo tossed 2 2⁄3 innings of scoreless relief but walked the bases loaded in the eighth. Robert Gsellman, who entered with one out, retired both of his batters to escape the jam.

In the second game, Corey Oswalt was perfect in the first four innings but walked the bases loaded (one intentional) in the fifth and yielded a three-run double by Phillies righthander Aaron Nola.

After Flores’ ninth-inning double, Michael Conforto walked, putting two runners on, but Devin Mesoraco struck out to end it.

Callaway attributed the Mets’ recent offensive struggles — five runs in four games — to good pitching. “Really good pitchers making really good pitches,” he said. “They held us at bay.”

Most walk-off home runs in Mets history:

4 Wilmer Flores

Cleon Jones

Chris Jones

Kevin McReynolds

Mike Piazza

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