Pittsburgh’s Carlos Santana is congratulated by teammates after hitting his first home run of the season Wednesday, helping the Pirates beat the Red Sox at Fenway Park, 4-1. Steven Senne/Associated Press

BOSTON — Mitch Keller struck out seven, Carlos Santana homered and Bryan Reynolds knocked in his seventh run of the season as the Pittsburgh Pirates completed a three-game sweep of the Red Sox with a 4-1 win Wednesday.

Ke’Bryan Hayes drove in a run with a perfectly-placed bunt in the sixth, and Santana added an RBI double during a two-run seventh that put the Pirates up 4-0.

It was the Pirates’ first road sweep of an American League opponent since Pittsburgh took three at Detroit in 2018.

“That’s a good Red Sox team and they score a bunch of runs. I was really proud of our pitchers and how they did a good job of neutralizing them,” Pirates Manager Derek Shelton said.

Pittsburgh improved to 4-2 on a cold, gray and blustery afternoon at Fenway Park, where the game-time temperature was 41 degrees. The Red Sox fell to 2-4.

Keller (1-0), wearing short sleeves despite the conditions, held Boston to one run on four hits, striking out seven and walking two. He carried a shutout into the seventh, when Triston Casas doubled with two out and scored on a single by Christian Arroyo.

“We had used a lot of our leverage guys (in the first two games of the series) and were a little short,” Shelton said. “For him to give us seven strong and finish was really important. Outstanding outing by him.”

Boston’s Corey Kluber (0-1) held the Pirates to one run on three hits over five innings. The only run charged to Kluber was in the fourth, when Santana pounced on an inside cutter and drove it out to right for his first homer of the season, giving the Pirates a 1-0 lead.

John Schreiber started the sixth for Boston and faced Reynolds, who had homered in three straight games. He lined Schreiber’s first pitch for a double to left. Reynolds took third on an infield single by Andrew McCutchen and scored easily when Hayes dropped a bunt just a few feet inside the first-base line and ran it out for an infield hit.

Duane Underwood threw just five pitches in the ninth for his first save.

FURTHER REVIEW

Keller and the Pirates had to weather a brief scare when a drive to right by pinch-hitter Reese McGuire with two on in the seventh was initially called a home run, which would have tied the game. The umpires briefly met and concluded it was foul, which was confirmed on a video review.

“That was kind of a crazy turn of events there,” Keller said. “I was watching the ball. I was kind of amazed that they called it fair.”

SOX SPUTTER

After taking a 1-0 lead in the first inning of Tuesday night’s 4-1 loss, Boston didn’t score again until the seventh inning on Wednesday.

“We didn’t play good baseball,” Manager Alex Cora said. “We show some flashes of good stuff, but overall, like today, that wasn’t good. When you aren’t scoring runs like the last two days, you’ve got to be on point. Even when you’re scoring runs, you’ve got to play better defense. I think we just made some bad decisions.”

REYNOLDS’ ROLL

Although his streak of consecutive games with a homer ended at three, Reynolds continued his torrid start. He was 7 for 12 in the series and has 24 total bases through six games. The only Pittsburgh player with more in the first six games was Barry Bonds in 1988.

TRAINER’S ROOM

Pirates: Shortstop Oneil Cruz needed a few minutes with a trainer after getting tangled up with Rafael Devers while sliding into third on a throwing error in the seventh. Cruz remained in the game through the rest of the top half of the inning, but was replaced at short by Radolfo Castro when Boston came to bat.

Red Sox: Right-hander Brayan Bello (right elbow inflammation) threw 72 pitches Wednesday in a rehab start in Fort Meyers, Florida, and reported no issues, the Red Sox said.