Mets starting pitcher Taijuan Walker delivers against Atlanta during the...

Mets starting pitcher Taijuan Walker delivers against Atlanta during the first inning of an MLB game at Citi Field on July 29. Credit: Kathleen Malone-Van Dyke

PHILADELPHIA — When the simple act of swinging a bat caused problems for Taijuan Walker, including a May stay on the injured list because of side tightness and more recent discomfort in his non-throwing shoulder, the Mets figured out a fix: Bat from the other side.

That is why Walker recently has been practicing as a lefthanded hitter and even batted that way in his most recent start. He plans to do it again Sunday against the Phillies.

Doing it that way does not trigger pain or soreness, which is improvement and speaks to how low the bar is for pitchers at the plate. And it gives him a puncher’s chance — or a pitcher’s chance — of making contact.

"It’s going good. I can swing, so that’s good," Walker said. "I couldn’t really swing righty, so swing lefty, hopefully put the ball in play and see if anything will happen."

A righthanded pitcher, Walker always has been a righthanded hitter, too. But recently his left shoulder — the lead shoulder as he awaited a pitch — would hurt a bit because of the motion made when he finished a swing.

He said it has not contributed to his 12.00 ERA in four starts since the All-Star break, but it still required addressing. When it popped again three starts ago, the immediate solution was don’t swing at all. In his next outing, he bunted in non-bunting situations, such as with two outs, two strikes or both. Then came the idea to hit lefty.

Depending on how comfortable he feels, he still might bunt righty, swing lefty. But he plans to shift all of his batting activity to the other side sooner rather than later.

And then, later, maybe not hit at all. MLB and the players’ union are due to negotiate a new collective bargaining agreement ahead of the 2022 season, and it might include bringing the DH to the National League permanently.

Such a rule change would be welcomed by Walker and others. Jacob deGrom attributed four of his six injuries this year to swings.

Walker has had enough of pitchers hitting.

"I think everyone has," he said, adding with a laugh: "I was all for it, and now I’m like over it. I’m tired."

Diaz back

Edwin Diaz returned to the Mets on Friday after a two-day paternity leave, arriving at the ballpark less than two hours before first pitch.

He allowed a two-run homer by Bryce Harper in the eighth inning of a 4-2 loss to the Phillies. Manager Luis Rojas said he wanted Diaz in the game despite the non-save situation because he hadn’t pitched since Saturday.

"He usually gets really, really bad command-wise when he doesn’t pitch after five days," Rojas said. "We were looking to get him in there."

Diaz’s wife, Nashaly, gave birth to their second child, Sebastian, on Wednesday.

The Mets optioned righthander Jake Reed to Triple-A Syracuse to make room on the roster for Diaz.

Catching up

Catcher Tomas Nido started for the 10th time in the past 20 games. James McCann, who has played nearly twice as many games as Nido this year, started the other 10. Said Rojas, "I don’t want to say splitting time, but Nido’s getting more playing time because we want to keep him active."