NEW YORK -- Right-hander Taijuan Walker pitched his last game of the regular season and gave the Phillies much-needed length. However, a slow start led to a 4-3 loss against the Mets in Game 1 of a straight doubleheader at Citi Field on Saturday.

The majority of Walker’s problems occurred in the first inning. He threw 22 pitches during that frame as New York scored three runs. With runners on first and third, Pete Alonso grounded out, but Rafael Ortega scored the first run of the game. Three batters later, Brett Baty laced a two-out single to right field, sending Ronny Mauricio to the plate. With Luis Guillorme in the batter’s box, Walker threw a wild pitch that allowed Francisco Lindor to score the third run of the inning.

• Games remaining (2): at NYM (2)
• Standings update: The Phillies (89-71) clinched the top National League Wild Card spot. They will host a Wild Card Series against the No. 2 Wild Card.

After allowing a leadoff homer to Omar Narváez to start the second inning, Walker settled down and made it through seven innings, striking out three batters while walking four. It helped that he fixed his mechanics by the fourth inning.

“I wanted to feel some things in my mechanics,” said Walker. “I felt there was some [velocity] in the tank. I was trying to figure out some stuff in the lower half and upper half [of my body]. … By the fourth inning, I got back in sync with my mechanics. I felt a lot better. Those last four innings felt really good.”

Walker had a good first year in Philly, winning a team-leading 15 games with a 4.38 ERA and setting a career high with 172 2/3 innings.

“There were a lot of ups and downs,” Walker said. “I wasn’t as consistent as I wanted to be, but I was glad I was able to give some good innings, make every start. That was a huge goal for me. First year, new team. I felt pretty good.”

Walker is looking forward to making his first postseason appearance since 2017, when he was with the D-backs. He pitched one inning out of the bullpen against the Dodgers and allowed four runs. 

“We have a really deep team. We saw it the last couple of games,” Walker said.

The Phillies were no match for Mets right-hander Tylor Megill, only collecting four hits in his 7 1/3 innings of work. But Philadelphia managed to score its first run in the eighth, when Edmundo Sosa blooped a single to left field off left-hander Brooks Raley, allowing Weston Wilson to score.

Philadelphia threatened with a ninth-inning comeback, plating two runs and bringing the potential go-ahead run to the plate against right-hander Adam Ottavino. However, Cristian Pache flied out to center to end the game.