PHILADELPHIA — The Mets were without their starting pitcher after just two innings against the Phillies, spelling disaster for the bullpen to cover the remaining seven frames. Despite David Peterson carrying the load, his strong effort in relief went from a turning point to a spoiled performance.

Taijuan Walker exited his first start of the year after two perfect innings with what the Mets are calling right shoulder irritation. Then Peterson, who entered in the third, ate the middle innings and dominated the Phillies lineup. But it wasn’t enough. For the second-straight day, an ugly eighth inning and a late rally sealed a Mets loss.

Once Trevor May became the second Mets pitcher on Monday night to leave his outing with a physical issue, the bullpen could not stop the bleeding. J.T. Realmuto cranked a two-run home run off left-hander Joely Rodriguez. Then Rhys Hoskins and Didi Gregorius collected back-to-back RBI doubles to complete a five-run rally and hand the Mets a 5-4 loss in the series opener at Citizens Bank Park.

Peterson’s four scoreless innings were, at least, one bright spot of Monday’s bullpen meltdown. The left-hander threw four scoreless innings and allowed just three hits against a tough Philly lineup. Peterson struck out leadoff hitter Kyle Schwarber both times he faced him, stifling one of the biggest threats in the Phillies order. The southpaw escaped a jam in the fourth, with runners on first and second, thanks to a key double play and impressive defense from second baseman Luis Guillorme.

It was all coming up roses for Peterson, who looked like a different pitcher than the Mets saw last year.

But the same could not be said for May, who took the ball from Peterson in the seventh. He kept the Phillies off the scoreboard in one inning of work, but Mets manager Buck Showalter asked May to pitch one more, something the right-hander never did in 2021. After walking his first batter of the eighth, May left the game with an apparent injury.

The sudden bout of shoulder irritation is a troubling development for Walker, who also had an early exit from his last start of spring with right knee soreness. It’s possible Walker, while trying not to put weight on his knee, wound up putting too much pressure on his arm, leading to that pain popping up in his pitching shoulder. But shoulder and arm injuries are never a good sign.

Shoulder issues aside, Walker’s stuff looked terrific on Monday as he retired all six batters he faced, including strikeouts to Kyle Schwarber, Bryce Harper, Nick Castellanos and Didi Gregorius. Walker went to his splitter almost just as much as he used his fastball and slider. It worked, as Phillies hitters swung and whiffed at all seven splitters Walker offered on Monday.

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