David Peterson is used to seeing things happen to the...

David Peterson is used to seeing things happen to the pitching staff and understands he has to be prepared. Credit: Newsday/Alejandra Villa Loarca

WEST PALM BEACH, Fla. — David Peterson didn’t know why and he didn’t know when, but he knew this would happen again.

The Mets will need Peterson — or someone — to step into the rotation during the indefinite absence of lefthander Jose Quintana, who was diagnosed with a rib stress fracture Monday. Peterson entered camp slotted into approximately the No. 6 spot on the five-man rotation depth chart. Now, there is an opening.

This is normal for him — majors or minors, rotation or bullpen, changing direction whenever told, at the mercy of other variables well outside his control. This unpredictable role is not his preferred job, but it is the one he has and the one he tries to do well.

Manager Buck Showalter said at the start of spring training that Peterson and Tylor Megill would be needed in the majors, even if their path to a spot was unclear then. And here the Mets are, still a few weeks from Opening Day.

“There’s been a lot of attention as to the average age of our rotation,” Peterson said Tuesday. “But you look at last year, when we didn’t make it out of spring training with five healthy starters. So I don’t think (being told to stay ready) really needed to be said. We understood where we stand and yeah, the likelihood of those five guys making 30 starts each is highly unlikely. At some point, something is going to happen. We saw that last year and you see it every year . . . Come in and do my work and help contribute how I can.”

Peterson completed a bullpen session Tuesday afternoon, his first since being struck in the left foot by a batted ball Saturday. He said he is sore but not limited in his pitching activity. The Mets had him penciled in for a game Thursday but pushed him back to a day to be decided.

Showalter did not provide an update on Quintana, who had travel issues on his way back to New York, where he is to undergo further testing.

“When we’ve got a guy that’s been as healthy as he has, you’re used to having (minor physical) things that you just go pitch and it’s not really an issue,” Showalter said. “You’re hoping for a little better news. But it’ll heal and it’ll pass and he’ll pitch for us.

Extra bases

Rule 5 pick Zach Greene walked a batter and allowed two hits, including a tying two-out, three-run home run, in the ninth inning of the Mets’ 5-5 tie with the Astros. Showalter pulled him immediately after. Greene has had consecutive ugly outings (following two solid ones) . . . Darin Ruf made his Grapefruit League debut, going 0-for-3 with two strikeouts and playing five innings at first base. He had been slowed by arthritis in his right wrist, which required a cortisone shot. Showalter said that “in a perfect world” Ruf will see time at first and in the outfield during camp . . . Joey Lucchesi, also appearing in his first exhibition game, lasted just one inning because of a high pitch count. He was scheduled for more. Carlos Carrasco (three innings, one run) and Tylor Megill (2 1/3 innings, no runs) were better . . . Infielder Danny Mendick, who tore the ACL in his right knee in June, is scheduled to play about three innings Wednesday in his first exhibition game.

DON'T MISS THIS LIMITED-TIME OFFER1 5 months for only $1Save on Unlimited Digital Access