Decision day is looming for Steven Matz, who has been rehabbing his left shoulder at the team’s minor-league complex in Port St. Lucie, Florida.

With Jacob deGrom out of the mix, manager Terry Collins would like to enter the final two weeks of the regular season with a stable five-man rotation. When asked who will join Noah Syndergaard, Bartolo Colon, Robert Gsellman and Seth Lugo, Collins said, “We have no plans yet. Nothing’s written. Steven Matz’s name is [assumed] to be in the mix.’’

Matz, who was diagnosed with a shoulder impingement, threw Friday, but there is no timetable yet for him to rejoin the Mets. “I think [Monday] when he shows up, we’ll know more,’’ Collins said, “but we certainly hope that this week he’s up here with an opportunity to pitch.’’

Collins said it will take time to build up Matz’s arm strength and suggested the time required for that is growing short. Matz (9-8, 3.40) has not pitched in a game since Aug. 14. He already had been pitching with a bone spur in his left elbow and likely is headed for offseason surgery to alleviate the discomfort.

Walker on the mend

Second baseman Neil Walker, who had back surgery earlier this month, is looking forward to rehabilitation and returning to the Mets next season if the sides can work out a deal.

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“I feel better now than I did before going into surgery,’’ he said. “That’s always a good thing, so I created some relief. Strength already is coming back in my legs. It’s been good . . . ’’

Walker can become a free agent but indicated the Mets would be his first choice. “I mean, this is a great fit,’’ he said. “Looking around, it’s a really good fit for me. I’ve enjoyed my time here this year.”

Before Walker’s surgery, general manager Sandy Alderson said he would entertain talks about re-signing Walker before he hits free agency. Walker said there have been no such discussions, but “we both expressed we’re looking forward to having conversations down the line.’’

Duda hitless in return

First baseman Lucas Duda, who had been sidelined since May 23 with a stress fracture in his lower back, went 0-for-2 with a strikeout in his return to the lineup. He was removed for a pinch hitter in the sixth inning. Collins said Duda looked “like he hasn’t played in four months. He said the game’s pretty fast up here.’’