Chapman says sore knee is fine

When Aroldis Chapman has to back up a base or make a quick move off the mound, it is easy for the Yankees to see there is something bothering the left knee that supports a chiseled upper body that looks more like an NFL safety’s than it does a pitcher’s.

Following Friday night’s 4-1 win over the Mets in the Subway Series opener at Citi Field, Chapman said he has been dealing with tendinitis for about three weeks.

It is something the Yankees have been monitoring, but Aaron Boone said the problem wasn’t bothering Chapman’s pitching.

“I don’t think it’s that much of a concern. It’s been something he has been dealing with,’’ the manager said of the pelletthrowing lefty who led AL relievers with a 15.53 strikeout-pernine innings ratio entering Saturday night’s 4-3 win over the Mets. That was second in the majors among all pitchers.

The knee issue didn’t keep Chapman from closing the comefrom-behind victory and posting his 17th save by getting the final three outs Saturday when he fanned pinch-hitter Devin Mesoraco with a 101 mph fastball, had four more pitches of 100 mph or higher and locked Jose Bautista’s knees with a 3-2 slider for strike three. Chapman was third among AL relievers in saves entering the game.

GM Brian Cashman shared Boone’s lack of major concern.

“Low because it’s something he’s been dealing with for a while and doesn’t feel it pitching,’’ Cashman said.

Aaron Hicks was surprised to watch his leadoff drive to right-center roll through an open door leading into the Yankees’ bullpen Saturday.

“It’s one of those situations before the game starts that it’s locked up and done with,’’ said Hicks, whose hit was ruled a ground-rule double but could have been a triple if it hadn’t gone out of play. “I could tell, I noticed the outfielders with their hands up.’’

Boone was puzzled by the door not being shut.

“That’s a good question,’’ Boone said when asked how the door stayed open. “We will make sure it’s secure [Sunday].’’

Aaron Judge failed to advance Hicks with a ground out to the left side and Giancarlo Stanton struck out looking. With the frigid Gary Sanchez at the plate, Hicks broke from second intending to swipe third. Instead, Steven Matz turned and caught him going back to second.

“If you try to steal, you have to be 100 percent sure,’’ Hicks said. “I felt it was the right time to go. Obviously, it wasn’t.’’