BALTIMORE -- Frustration had to be the word Chris Sale was muttering into his glove as he walked off the mound following a shaky bottom of the fourth inning, in which the remainder of the early cushion his team provided for him whittled away to nothing.

As Sale got back to the dugout, he spiked his glove onto the bench, then punched a cooler with his right (non-throwing) hand four times.

Yes, Boston’s lefty was filled with frustration with his fourth subpar outing in his five starts this season as the Red Sox lost to the Orioles, 5-4, on Monday night at Camden Yards.

Sale (1-2, 8.22 ERA) wishes he could put a finger on it. At this point, all he can do is keep searching for solutions.

“It was just bad. I wish I had more for you. I really do,” said Sale. “It sucks to work this hard and get nothing in return, you know? I’m putting in the work. It’s just not showing up. Again, I could sit here and try to find something, but it's pretty black and white. You either get it done or you don't. Unfortunately, for the most part this year, I haven't gotten it done.”

Early on, it looked like this would be a big night for the Red Sox. Triston Casas hit a mammoth homer to right that traveled a projected distance of 426 feet to open the scoring in the second. And an inning later, Rafael Devers became the seventh Boston player to put one onto Eutaw Street (and first since Jackie Bradley Jr. in 2017) with a 115 mph scorcher.

But the good feelings drifted away swiftly, as Sale couldn’t hold the 4-0 lead his team staked him to through the top of the third inning.

“Definitely disappointing,” said Sale. “Guys come up quick, come out hot, give me a four-run cushion, and I just [give] it away. That’s tough.”

This misstep by Sale was particularly perplexing because he was coming off a vintage outing last week against the Twins, when he had 11 strikeouts while allowing just one run on three hits over six innings.

Instead of carrying over the momentum, Sale lost it all, failing to strike out a batter for the first time in his career. The only other start Sale had with a goose egg in the K column was July 22, 2022, when he broke his left pinkie finger at Yankee Stadium after recording just two outs.

What does the lack of a punchout for the first time in a non-injury start for the first time in his career tell Sell?

“It tells me I sucked,” Sale said.

His catcher, Connor Wong was less harsh.

“I thought it was quite a weird outing,” said Wong. “They put some swings on some tough pitches. Got some bloop hits, and it kind of snowballed from there. We will just have to go back and watch the film and try and process that.”

One thing that is clear is that Sale’s slider at this point of 2023 isn’t close to what it once was.

The expected wOBA -- projected wOBA based on the quality of contact, strikeouts and walks -- against Sale’s slider has dramatically increased (or gotten worse). It was at .294 this season entering Monday’s start compared to .159 in 2018.

Mainly to preserve the bullpen, Red Sox manager Alex Cora had Sale go five innings on Monday. He gave up five runs on nine hits and one walk on 83 pitches.

Of the 42 swings the Orioles took, they missed just twice. It was in stark contrast to that brilliant last start, when Sale got 19 whiffs out of 44 swings by the Twins.

After three consecutive seasons in which he was mostly either injured or rehabbing from an injury, Sale’s rust has been noticeable thus far in 2023.

His next start is likely to be Sunday at Fenway Park against the Guardians.

“You’ve just got to keep working. But this ain’t the Try-Hard League. This isn’t the Do-Good League,” said Sale. “People only care so much about trying hard, working hard. It’s got to be out there when the lights flick on. I’ve got to step up. I’ve got to find a way. That's who I am. That's who I have to be.”