BOSTON — After being hopeful Aaron Hicks would be back this month from a flexor strain near his right elbow, Yankees manager Aaron Boone said Saturday the center fielder now may be gone for the year following a setback in his rehab in Tampa.

“He’s slowed down,’’ Boone said before the Yankees defeated the Red Sox 5-1 at Fenway Park. “He’s not feeling quite right.”

Hicks has been out since being pulled from a game on Aug. 3 against Boston after making a throw to third base. He began a throwing program in The Bronx during the Yankees’ recent homestand and was scheduled to continue that — and start hitting — in Tampa in the coming days.

Instead, Hicks had another MRI exam, one that — according to Boone — showed no ligament damage.

“Everything checked out really well,’’ the manager said. “It was encouraging, but he’s still not quite where he needs to be to start ramping up [activity].”

Asked if the news meant Hicks’ season could be in jeopardy, Boone said: “It could be. We’ll see how the next several days unfold. But as of right now, he hasn’t been able to advance.”

It’s the latest development in a season full of injuries and setbacks that has cast a shadow over an otherwise excellent regular season.

Hicks missed the first month of the year with a back injury and hasn’t been especially productive even when he has been on the field.

Hicks will turn 30 next month and signed a seven-year, $70 million deal during spring training.

After throwing last week for the first time since the flexor strain injury, Hicks said his arm felt “weird,’’ but that he was OK physically.”

Boone said Hicks didn’t complain of pain, but that he wasn’t able to “let it go” when he threw.

And though the manager added the flexor strain appears to be healed, he added Hicks might get a second opinion.

In the meantime, Hicks will be shutdown indefinitely, and it’s anyone’s guess when he might return.

The potential loss of Hicks figures to be put even more of a spotlight on Giancarlo Stanton, who has also been working in Tampa. Stanton, who has been limited to nine games this season, first by a torn biceps and then by a shoulder injury before a sprained right knee sidelined him, is expected to play more simulated games this weekend.

“Everything went well with his agility,’’ Boone said of Stanton’s work on Friday. “I think he’s just building up to the point where he can play in a game.”

And he reiterated the fact he expects Stanton to be able to play the outfield if and when he does get back to the Yankees.

With Cameron Maybin still dealing with an unidentified left wrist injury that has kept him out of the starting lineup since Aug. 28, the Yankees are again down to four healthy outfielders: Brett Gardner, Mike Tauchman, Aaron Judge and Clint Frazier.

Boone said it was “reasonable to think [Stanton] can get a decent amount of at-bats late in the year. We’ll just see.”

But the Yankees are running out of time — and games — to find out.

And though Judge and Gardner have played well of late, Tauchman has faded a bit at the plate and the Yankees would no doubt like to get Gardner rest before the playoffs begin.