Five Phillies had crossed home plate in the first inning Saturday night when Terry Collins walked out to go get Sean Gilmartin. The chorus in the stands at Citi Field serenaded the lefthander with boos on the way to the dugout after he managed to record all of two outs in this fill-in start.

The Mets have been doing their best to overcome the vast array of health issues to hit the rotation, but their depth has been taxed.

Even if they draw a wild card and then advance, they would have a vulnerable-on-paper rotation. It would be fronted by Noah Syndergaard, who was scratched from this start due to a strep throat, and Bartolo Colon before untested-in-October rookies Seth Lugo and Robert Gsellman become the primary candidates to start.

One of the missing tested-in-October pitchers spoke to reporters before the game Saturday for the first time since undergoing surgery on Wednesday. The Mets really could use Jacob deGrom, but it’s about next year for him now. The 28-year-old righthander sounded in good spirits after having the ulnar nerve repositioned in his pitching elbow.

“It looked like it definitely needed to be moved, and they were happy with the results,” he said.

Matt Harvey underwent season-ending surgery in July. Steven Matz is looking like a relief option at best if he can return from his shoulder problem. But for deGrom, it’s about incremental steps so he’s good to go by the time spring training rolls around in February.

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“Next is getting the stitches out,” deGrom said. “They said I could move it as much as I want . . . I’m just waiting so I can start physical therapy. So I think once the stitches [are] out, then I think they said maybe two weeks I start doing stuff, strengthening it.

“I can’t full straighten it yet . . . But it feels good now. It’s not sore at all.”

DeGrom received some reassuring words from Hall of Famer John Smoltz, Mets broadcaster Ron Darling and the surgeon, Mets medical director Dr. David Altchek.

“I talked to Smoltz and Ron Darling texted [a team official] and said that he had it,” deGrom said. “He had it in November and he was ready for spring training. Talking to Dr. Altchek, he said it looked like it needed to be done, and I should be fine.”

So his final numbers came out to 7-8 with a 3.04 ERA in 24 starts. He was shut down after a start on Sept. 1. He was supposed to return last Sunday but he felt pain throwing a ball back toward the infield during batting practice following a bullpen session two days earlier. He has said the problems dated to five or six starts back.

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“I felt kind of numbness in the fingers; I didn’t really think anything of it,” said deGrom, who missed the 2011 season in the minors after undergoing Tommy John surgery. “It turned into kind of a pain in the elbow. All the MRIs came back and the ligament was fine. So with my symptoms, talking to the doctors, they said the next thing is the nerve.

“It’s reassuring that when they got in there that they could tell where it was getting aggravated and kind of ‘compressed’ was the word [Altchek] used . . . It’s right by the ligament, so he actually had his eyes on the ligament, too. He said that all looked great. So that’s very comforting.”