Right-hander Garrett Whitlock is day-to-day with left knee soreness after slipping on the mound during Sunday’s rain-soaked series finale against the visiting Minnesota Twins.

Boston Red Sox interim manager Chad Tracy revealed the ailment pregame Wednesday, when a reporter asked why fellow righty Justin Slaten had warmed up in the bullpen before the eighth rather than Whitlock, who’s established himself as one of the premier set-up men in baseball.

“There’s a little something going on with Whit,” Tracy said. “Some soreness in the knee, so we got to just keep an eye on that and see where we’re at. … It was a brutal day, brutal conditions.”

Whitlock clarified that he hurt his knee on “the very first warm-up pitch” when he took the mound for the sixth inning on Sunday.

“Obviously the conditions were super wet, kind of slipped and hyperextended my knee and everything,” the veteran righty echoed. “I was like, ‘Man, that didn’t feel good.’ … And it was kind of in my head, and then I saw the clock going, I was like, ‘Oh wait, they didn’t stop it, I need to keep throwing.’

“And so yeah, I probably should have taken some time to be like, ‘Alright, slow things down,’ but that’s part of it. You’re just trying to compete and everything, and I’m never going to make excuses. I still gave up runs and everything.”

The slip set the stage for Whitlock’s first blown save of the season. He recorded just one out (via strikeout), and allowed an earned run on two hits. The performance, in his 20th appearance of the year, pushed his ERA from 2.79 to 3.20. The Twins won 6-5, completing their first sweep of the Sox at Fenway Park since 1994.

Imaging was negative for structural damage, so the Red Sox are trying to avoid putting Whitlock on the injured list, though Tracy admitted it puts them in a tight spot.

“Obviously that’s a challenge with the middle relief being where it’s at, but as of now yeah, we just got to keep assessing and see where it’s at,” Tracy said. “Sometimes there’s nothing structurally wrong but if you slip and kind of jam you still have some soreness.”

Whitlock threw in the outfield during afternoon workouts, but said the soreness has only slightly abated since Sunday.

“I’d say it’s probably the same right now,” he said, but then amended his answer. “I’d say today it was a little bit better than the last two days. That’s for sure.”

Asked if he was available to pitch that night, Whitlock said, “I’m going to let them come up with that, obviously, I’m gonna give it everything I can. But yeah, it’s still pretty sore.”