NEW YORK -- Boston Red Sox ace Chris Sale says he's "as frustrated as I've ever been on a baseball field," calling his performance this season "flat-out embarrassing" following an 8-0 loss to the New York Yankees on Tuesday night.

While Sale flashed the high-powered fastball and biting slider that defined him as he established himself as one of the game's best pitchers, Yankees hitters still tuned him up for four runs in five innings. Sale's season ERA dropped to 8.50, and he suffered his fourth loss of the year, matching his total for the entire 2018 season.

"I just flat-out stink right now," the winless Sale said. "I don't know what it is. When you're going good, it's good. When you're going bad, it's pretty bad."

Pitching at Yankee Stadium on six days' rest, Sale cruised through the first two innings, with his fastball topping out at 97 mph after languishing in the low 90s in his first three starts. A pair of two-out, run-scoring singles in the third from DJ LeMahieu and Luke Voit plated the Yankees' first two runs. An inning later, outfielder Clint Frazier whacked a hanging Sale changeup out to right field -- the fifth home run that Sale has allowed in 18 innings this season -- and rookie Mike Tauchman doubled home another run to stake James Paxton a healthy lead.

Paxton didn't need much. He won the battle of hard-throwing left-handers, striking out 12 and allowing two hits over eight shutout innings.

As Boston's record dropped to 6-12, the Red Sox tried to keep perspective on their perplexing start following a World Series title. Manager Alex Cora took solace in the return of Sale's raw stuff, expecting that it would lead to more come his fifth start this season.

"I don't want to say it's a work in progress, because we're not here to build up," Cora said. "I'm not going to be surprised if, in his next outing, he's right where we need him to be. ... He's very close to the 'real' Chris Sale."

Sale did not take the same solace. Even as his looping slider held the Yankees at bay, New York teed off on his fastball, going 5-for-8 in at-bats that ended with the pitch.

"Doesn't matter how hard you throw or how fancy it looks," Sale said. "You need to throw up zeros."

Sale is far from the only Red Sox pitcher who has struggled to do so. Boston's team ERA this season is 6.09. The Red Sox have allowed a major league-leading 114 runs. The Red Sox's minus-40 run differential is the worst in the American League and only three runs ahead of the Miami Marlins'. Boston's offensive struggles have only compounded the pitching travails.

In better times, Sale was the salve for such troubles. On the eve of the season, the Red Sox signed him to a five-year, $145 million contract extension that begins in the 2020 season. However concerned the organization might have been about Sale's shoulder troubles last season or low velocity in spring training, it did not intend to let the left-hander reach free agency this winter.

Now, Sale is in the midst of what he called the worst stretch of his 10-year career, which has included six consecutive top-5 finishes in AL Cy Young balloting and, coming into the season, a 2.89 ERA, 103-65 record and 1,789 strikeouts in 1,482⅓ innings.

"I've got to find a way to pitch better," Sale said. "This is flat-out embarrassing. For my family, for my team, for our fans. This is about as bad as it gets. I have to pitch better. I keep saying the same things, but at the end of the day, you go out there and give up four runs here, five runs here, seven runs here ... if I get into the sixth or seventh inning like I should -- that's who I am.

"I'm supposed to pitch into the sixth, seventh, eighth inning, finish games and stuff like that, save our bullpen, cut it off when we're losing and keep winning streaks going. That's not who I've been."

Asked if, as Cora said, the "real" version of him is coming, Sale said: "You'd better f---ing hope so."