BOSTON — Dellin Betances stretched out to throwing to 90 feet on flat ground Thursday at Fenway Park, as he makes his way back from the IL with the hope of returning at some point this season.

“I threw 25 [pitches] at 60 [feet], 20 at 75 and five at 90,’’ said Betances, who hasn’t pitched yet this season thanks to an impingement in his right shoulder and a lat strain in the area. “I am off [Friday] and I think I will go back to 90 feet on Saturday. I have no idea after that. It’s obviously [going] slow but the progress is what it is. Taking a lot of time but we can’t rush it, but it has been going good, though.’’

When the Yankees placed Brett Gardner on the IL on Thursday, they recalled lefty reliever Stephen Tarpley from Triple-A Scranton/Wilkes-Barre.

That gave the Yankees 14 pitchers and just three outfielders. Tarpley gave up four runs and five hits in 1 ²/₃ innings in the Yankees’ 19-3 blowout loss to the Red Sox and was sent to SWB after the game.

Aaron Boone started Kyle Higashioka behind the plate Thursday.

Austin Romine entered Tuesday night’s game to replace Gary Sanchez, caught all nine innings Wednesday night and arrived with his teammate at their hotel here at 5 a.m. arrival Thursday.

Boone said he would likely alternate the catchers across these four games, though Romine pitched an inning in relief and gave up three runs on four hits in ther blowout. Higashioka had a homer.

Watching Edwin Encarnacion — who had fouled a ball off his left foot earlier in the at-bat — hobble around the bases after hitting a home run against the Twins on Wednesday night, there was legitimate concern the DH wouldn’t be able to play Thursday. Yet, Encarnacion was in the lineup hitting fourth and went 0-for-4.

His homer Wednesday night was his 30th of the season (21 with Seattle; nine with the Yankees) and the eighth straight season in which he has hit at least 30.

The 19 runs and 23 hits given up by Yankee pitchers in Thursday’s 19-3 loss at Fenway Park were the most in each category this season. The 19 runs surrendered to the Red Sox is the most since 1913.