Gunnar Henderson opened the Orioles’ six-run 10th with a two-run homer against Isaiah Campbell (0-1), scoring automatic runner Jackson Holliday.

“We do have confidence in our offense,” Orioles manager Brandon Hyde said. “We can do a lot of different things and so far this year we’ve taken great at-bats the last third of the game.”

Campbell took the blame.

Cowser hits first 2 big league homers, Orioles beat Red Sox 9-4 in 10 innings for 3-game sweep - What's Up Newp

“Just didn’t do my job,” he said. “Can’t leave too many pitches over the plate against these guys. They hit them hard. They did their job. So, this loss is on me and just got to come in here and get better and get ready for the next outing.”

The 20-year-old Holliday, baseball’s top-rated prospect who made his big league debut a night earlier, scored two runs but went 0-for-4 for the second straight game.

Red Sox blow late lead, lose 9-4 in 10 innings as Orioles complete sweep

Cowser, another Orioles prospect who struggled during a brief stint in the majors last season, drove in 10 runs in the series.

“It came in a big spot today,” Cowser said. “Towards the end of the game, we started stacking good (at-bats), getting it to the next guy, and that’s something you have to do in a season like this.”

A night after the Orioles rallied from a 5-0 deficit to win 7-5, they fell behind 2-0 before coming back, thanks in part to some shaky defense by the Red Sox.

Cowser hits first 2 big league homers, Orioles beat Red Sox 9-4 in 10 innings for 3-game sweep

Boston led 2-1 when Holliday reached on an error by third baseman Pablo Reyes leading off the eighth. With one out, Adley Rutschman hit what appeared to be an inning-ending double-play grounder, but the Orioles challenged the call, and after a review, Holliday was ruled safe at second because shortstop David Hamilton missed the bag while making the turn.

“Yeah, we didn’t turn that double play,” Red Sox manager Alex Cora said. “But it was a good game, to be honest with you. We used everybody that was available, and we had to push Campbell there.

Get those brooms out: Orioles pull of series sweep of Red Sox

“But, it is what it is. It was a tough one. I liked the way we fought. We were there until the end, but, obviously a tough series and now we got to turn the page.”

Reliever Greg Weissert came in after the double play was overturned, and Anthony Santander hooked his first pitch around the foul pole in right for a two-run homer that made it 3-2.

Pinch-hitter Connor Wong tied it with two outs in the eighth with a homer over the Green Monster off Danny Coulombe. It was Wong’s first homer of the season and first career pinch homer.