NEW YORK -- Luis Severino's transformation into the Yankees' ace has taken place largely without interruption over the course of this All-Star campaign, and with the Red Sox in town, the right-hander picked an especially inopportune time to experience his worst outing of the season.
Andrew Benintendi hit a pair of three-run homers off Severino as Boston battered him for a career-high 10 runs (eight earned) in 4 1/3 innings, dealing the Yankees a 10-5 loss on Saturday at Yankee Stadium to reclaim a 4-1/2 game lead in the American League East race.
"This is a bad day," Severino said. "I have to keep working. I think I've got the Mets [next]. I've got to work hard and try to get the win."
Severino walked to the mound on Saturday riding a post-All-Star surge, winning his previous four starts while permitting one or no earned runs in each outing. He retired the first seven batters but then, beginning with a nine-pitch walk to Christian Vazquez, saw the next seven Red Sox reach base.
"He wasn't executing his pitches today," Yankees manager Joe Girardi said. "He made some mistakes. He's been so good and executing so well, we haven't seen it for a while, but it just goes to show you that he's human."
A key play in the five-run third inning was Eduardo Nunez's potential double-play grounder to third baseman Todd Frazier, who fielded the ball but fumbled the transfer as he rushed to try to turn two.
"Nunez is pretty quick, but you've got to be under control when you're fielding those balls," Frazier said. "At least get the one out. With two outs, it puts a little pressure on the other team."
Instead, Boston had the bases loaded and one out when Mookie Betts cracked a slider into left field for a two-run single. Pitching coach Larry Rothschild visited the mound, but Severino grooved a 1-1 fastball that Benintendi launched over the right-field wall to give Boston a 5-2 lead.

"You look at the first two innings, we weren't even having the ability to make adjustments," Red Sox manager John Farrell said. "He threw the fastball right at us. The couple of walks in the bottom of the order kind of opened the door a little bit for us, and then we were able to cash in."
Severino struck out the side in the fourth but had more trouble in the fifth, with the first three batters all scorching the ball at over 100 mph, according to Statcast™. Nunez singled, Betts doubled and Benintendi again visited the seats for a three-run blast that put Boston up, 8-3.
"He throws hard and has hard offspeed," Benintendi said. "You know whatever is coming is going to be hard. It's not easy to make an adjustment, but velocity kind of helps."
Mitch Moreland squibbed a double down the vacant third-base line and shortstop Didi Gregorius bounced a throw for an error before Severino's afternoon was mercifully complete. Rafael Devers then greeted Yankees reliever Giovanny Gallegos with a two-run double. The 10 runs allowed by Severino were the most by a Yankee since Sergio Mitre surrendered 11 (nine earned) on Sept. 6, 2009.
Though Severino has now completed 143 2/3 innings (just 7 2/3 innings shy of his 2016 total), Girardi said that it was too soon to entertain the question of if Severino may be running out of gas.
"I think if you put three or four [starts] back to back, then you wonder," Girardi said. "Every starter has a bad day. We've seen it for years and years and years. Right now, I don't see a lack of velocity. He just didn't have good stuff today. He wasn't as sharp as he's been."