Mike Tauchman was such an afterthought on the Yankees roster that when he returned to the dugout after blasting a three-run shot to the second deck to blow open an 8-0 win over the Red Sox, no one even realized it was the first home run of his career.

“He sat down next to me and told me it was his first home run,’’ Clint Frazier said.

Tauchman has been largely anonymous since arriving in a trade from Colorado late in spring training because the Yankees were in need of a fourth outfielder, with Aaron Hicks out with a back injury and Jacoby Ellsbury not close to taking the field.

He has stuck around, in part, because Giancarlo Stanton also has gone down with a biceps injury and the Yankees continue to say they like his defense.

But on Tuesday, Tauchman delivered a pair of huge hits.

The first came in the fourth inning with the Yankees up 3-0. Austin Romine singled with two outs to bring up Tauchman, a lefty swinger facing tough southpaw Chris Sale.

Tauchman came through with a double that got by a diving Mitch Moreland at first and went to the right-field corner, which allowed Romine to come around from first to make it 4-0.

Then, against right-hander Erasmo Ramirez in the sixth, with runners on second and third and one out, Tauchman blasted a shot into the second deck in right for a three-run homer that gave the Yankees a 7-0 lead.

Asked if he knew it was going out when he hit it, Tauchman paused and simply said, “Yes.”

Beyond that, though, he didn’t recall much from his trip around the bases.

“I wish I could tell you,” Tauchman said. “My mind was blank. I just tried to enjoy the moment and remember the feeling.’’

Tauchman had been just 2-for-16 and hadn’t driven in a run since being acquired in exchange for minor league pitcher Phillip Diehl.

But all four of his hits this season have been for extra-bases.

Because the Yankees have no choice but to rely on Tauchman for the foreseeable future, manager Aaron Boone is counting on Tuesday night being a sign of improvement from his entire team — and Tauchman.

“I hope he can get a little more settled in as he goes and gets more opportunities,’’ Boone said of Tauchman, who has started the past three games. “[Tuesday] wasn’t the easiest draw as a lefty against Sale there and he had really competitive at-bats. … He’s a talented player. We’ve known that … and [Tuesday] night, we saw a glimpse of his power at the plate.”