BOSTON -- With one out in the fourth inning and the Rays trailing by 10 runs, Josh Fleming handed the ball to manager Kevin Cash, walked off the mound, took a seat in the visitors’ dugout and stared out at the field. The left-hander had every reason to be frustrated after the worst outing of his young career, but he showed no sign of it.

The Red Sox hit Fleming early and often and didn’t let up the rest of the night, putting up another 10 runs after the Rays’ starter left the game. By the time it was all over, Boston’s lineup had set season highs in runs, hits and walks, and Tampa Bay’s five-game winning streak came to an end in an uncharacteristically ugly 20-8 loss at Fenway Park.

• Box score

“When your body feels that good and your arm feels that good and you don't see the results, it's difficult,” Fleming said afterward. “It's a difficult one to swallow.”

The Rays were down by 19 runs after eight innings -- three outs away from setting a record for the largest margin of defeat in franchise history -- but Brett Phillips hit his third grand slam of the season and Mike Zunino homered as they scored seven runs on five hits in the ninth against Red Sox right-hander Phillips Valdez. In the end, it was their most lopsided loss since a 15-1 defeat in Houston on Aug. 27, 2019.

“Games like this are going to happen,” Phillips said. “We need Flem to stay locked in and be the Fleming that we believe in and know he can be. So it's just a matter of putting some [games] like this behind us and showing back up tomorrow to take the series.”

With Ryan Yarbrough on the COVID-19 injured list and their banged-up bullpen used heavily of late, the Rays were hoping for a long outing from Fleming. Bumped up a day to start in place of Yarbrough -- albeit still working on six days’ rest -- Fleming instead gave up 10 runs on 11 hits and six walks over 3 1/3 innings.

Fleming said that he felt good physically but fell behind too often, left too many sinkers up in the zone and spun too many cutters over the middle of the plate. He tried to make the necessary adjustments on the fly, but the Red Sox left him no room for error.

“It's just one of those games that, when you fall behind against a team like the Red Sox, they're going to do damage,” Fleming said. “And, unfortunately, that's what happened tonight.”

Fleming’s outing went south from the start, as he gave up two runs on three consecutive doubles before recording his first out. The Red Sox tacked on another run in the first, then former Ray Hunter Renfroe drove in two more in the second to put Tampa Bay in a five-run hole.

Fleming stranded runners on the corners in the third and, having only thrown 52 pitches at that point, thought he’d at least be able to pitch deeper into the game. The Rays were hoping that would be the case ahead of what will essentially be a bullpen game started by Drew Rasmussen in Thursday’s series finale, but the fourth inning quickly got away from Fleming.

Rafael Devers doubled in a run with one out, then the Rays intentionally walked J.D. Martinez to load the bases, only for Fleming to walk Kevin Plawecki on four pitches. Marwin Gonzalez drove in another run on a single to right, and Bobby Dalbec plated two more before Cash emerged from the dugout to take the ball from Fleming.

“I had the zero in the third [and] I thought to myself, 'OK, that's what they get. I'm going to try to push for at least three more innings, maybe four if I have quick innings,’” Fleming said. “And that fourth inning came by, and just -- it's not a good inning.”

Left-hander Dietrich Enns picked up most of the remaining work after Fleming’s early exit, throwing 65 pitches over 3 2/3 innings. Cash was appreciative of Enns’ effort, noting that “his work saved the rest of the bullpen.”

To further preserve their relief arms during a stretch without an off-day until Aug. 23, the Rays sent catcher Francisco Mejía to the mound in the eighth. The Red Sox put up six runs, including three on a Xander Bogaerts homer, in his second pitching appearance of the season.

It wasn’t just a tough night on the mound, either. The Rays’ only run before their ninth-inning outburst came on Brandon Lowe’s 26th home run of the season in the sixth inning. Eovaldi shut down Tampa Bay’s scorching lineup before and after that, striking out 10 while allowing only three hits over seven innings.

The Rays’ issues extended into the field, too. With the bases loaded and two outs in the fifth, right fielder Randy Arozarena lost Bobby Dalbec’s high fly ball in the swirling wind. The ball, which had an expected batting average of .010 according to Statcast, fell for a bases-clearing triple that put the Red Sox ahead, 14-0.

“Lopsided losses happen, and we certainly had one tonight. We do a good job throughout the course of a long season of avoiding those, but tonight ... they just kept coming,” Cash said. “They were ready to go right out of the gate and attacked everything that Flem had and just put a bunch of runs on the board.”