BOSTON — The Boston Red Sox traded slugger Rafael Devers to the San Francisco Giants on Sunday in a deal that could shake up pennant races on both coasts.

San Francisco sent right-hander Jordan Hicks, lefty Kyle Harrison, outfield prospect James Tibbs III and minor league righty Jose Bello to Boston for the 28-year-old designated hitter, who had bristled at his demotion from third base this year.

The Giants are two games back of NL West-leading Los Angeles after losing 5-4 to the Dodgers on Sunday night.

Harrison was on his way to the bullpen to warm up for Sunday’s start when he was called back to the clubhouse and informed of the trade. Reliever Sean Hjelle was told about 30 minutes before first pitch that he would start.

“Yeah, it was a lot, and it was late, but you know what? This is something we really needed,” Giants manager Bob Melvin said.

“To get a guy like Devers … there’s a lot you have to give up for him, but this fits us perfectly. It’s a power left-handed bat, a guy that can go the other way and hit for power in our ballpark. I mean, it’s tailor-made for us, so kudos to the front office to swing this.”

Devers Has Hit 15 HRs This Season

A three-time All-Star who signed a 10-year, $313.5 million contract with the Red Sox in 2023, Devers is batting .272 with 15 homers and 58 RBIs in 73 games, including a solo shot in Boston’s 2-0 victory over the New York Yankees on Sunday that completed a three-game sweep.

But his relationship with the team began to deteriorate when the team signed Gold Glove third baseman Alex Bregman during spring training and asked Devers to move to DH; he balked before agreeing to the switch. When first baseman Triston Casas sustained a season-ending knee injury, the Red Sox approached Devers about playing the field and he declined, saying the front office “ should do their jobs ” and look for another player.

Buster Posey, a seven-time All-Star who took over as San Francisco’s president of baseball operations in September, said he reached out to Craig Breslow, Boston’s chief baseball officer, about two weeks ago. Trade talks picked up momentum over the past few days.

Which Position Will Devers Play?

Posey and Melvin declined to address what position Devers would play in San Francisco — “That’s a conversation for myself, Bob and Zack (general manager Zack Minasian) to have with him,” Posey said — but they are convinced Devers’ bat will have a significant impact on a lineup that has produced only 16 homers from the left side this season.

“We’re excited about adding one of the best hitters in all of major league baseball to our lineup,” Posey said. “We’re obviously taking on a lot of dollars, but there’s a belief that adding a guy like this puts us in a good position keep winning ballgames, get into the playoffs and try to win a World Series, which is our ultimate goal.”

The Giants have lacked slugging since Barry Bonds hit 45 homers in 2004; they are the only team in the majors who have not had a batter hit 30 homers since then. Devers has hit at least 30 homers in three different seasons.

“It’s tough losing (Harrison and Hicks) … but we’re getting a guy back who changes the lineup, who’s probably a top-10 hitter in baseball every year,” Giants pitcher Logan Webb said.

“Any time you add a player of that caliber, I think you give yourself a chance every day. I don’t know where he’s gonna hit, but I don’t think it really matters. The guy’s a stud, plain and simple. I’m excited about it.”