Giancarlo Stanton’s late-season slump has more to do with a timing problem than any lingering effects of a left hamstring injury that surfaced in the first week of August, according to Yankees manager Aaron Boone.

“I would say it is the timing. We saw a little bit of it early when he was fighting to get traction before he got going,’’ Boone said of the designated hitter on Thursday, before the Red Sox thumped the Yankees, 11-6, to win the AL East title for a third straight season. “The timing has been a little bit off.’’

Stanton’s timing reappeared in the fourth inning. After walking in the first and third, Stanton hit a grand slam off Heath Hembree that put the Yankees ahead, 6-4, and put sweep dreams in the Yankees’ heads.

Stanton’s 35th homer raised his RBI total to 93. More important, the Yankee have to hope he is ready to get hot and help carry them for the final 10 games, when they try to hold off the A’s and play the AL wild-card game at Yankee Stadium.

Boone said he doesn’t believe the hamstring issue is the reason that Stanton had homered just once in 59 September at-bats before Thursday night.

“I don’t think it’s much of a factor at all,’’ Boone said. “Obviously we have leaned on him heavily and there is no question this time of the year when he has played every day there is a fatigue factor, but I don’t think [the hamstring] has been much of a factor. There have been times when he has been a little sore — that’s when he has been at his best.’’

After hitting .323 (32-for-99) with five homers and 18 RBIs in July, Stanton fell to .267 but hit nine homers and drove in 20 runs in August. That was followed by what has been a miserable September, since Stanton is hitting .145 (9-for-62) with two homers and nine RBIs.