Clint Frazier got his first-ever postseason start on Monday against Tampa Bay left-hander Blake Snell.

His play in the ALDS Game 1 victory — which included a long homer to left — helped get him back in the lineup for Game 2, this time with Rays’ right-hander Tyler Glasnow on the mound, when Aaron Boone could have gone with lefty-swinging Brett Gardner.

“It’s something I slept on,’’ Boone said of the left-field decision prior to Tuesday’s Game 2 at Petco Park in San Diego. “It’s been that way each time [we’ve played].”

Boone pointed to the fact Glasnow has worse numbers against right-handed hitters than lefties, but just as important was the way Frazier swung the bat through much of the season — including on Monday, when he took Snell deep to open the third inning.

With Tampa Bay’s starters often looking to expand the zone, Boone has liked how both Frazier and Gardner have been able to swing at pitches in the zone — noting Frazier has “a chance to get on one,’’ as he did against Snell.

For all the success Frazier had at the plate when given the opportunity thanks to injuries to Aaron Judge and Giancarlo Stanton, along with the regression of Mike Tauchman, Frazier finished the regular season poorly.

He went 1-for-20 with 11 strikeouts in his last six games and had just one plate appearance in the wild-card series against the Indians, when he whiffed on three pitches.

But he shook that off in Monday’s win, hitting eighth, when he smacked the first of four Yankees home runs on the night before he was replaced by pinch-hitter Gardner with two outs in the top of the sixth against right-handed sidewinder Ryan Thompson.

“I definitely think it’s a good thing when you’ve had recent success to build on, especially when you’re a young player and hopefully it’s something he can ride and continue to build confidence from,’’ Boone said. “But I’m more banking on the fact he’s a really good player hitting down in the order who kind of epitomizes the good things about our team: He can control the zone and really hit.’’

Frazier has also hit right-handers well. And he’s shown that when he’s on, Frazier can be very dangerous.

He had stretches when he first got called up from the alternate site in August when he had seven hits in three games and also went 7-for-13 with four extra-base hits in a four-game stretch last month.

More than anything, Boone said, Frazier had “earned” the opportunity to start, in part to how he handled not seeing much action in the two-game sweep of the Indians.

“No doubt, as much as he’s meant to the team and the success he had for us and then not to play much those first two games and then go out and have immediate success, is definitely a confidence boost for a younger player,” Boone said.