Red Sox closer Kenley Jansen dealing with tight back, will not be available to pitch on Sunday

Red Sox closer Kenley Jansen did not look quite like himself on Saturday, and it turns out there is a logical reason as to why.

Coming into play earlier in the afternoon, Jansen had yet to allow a run through his first eight relief appearances (7 2/3 innings pitched) of the season. The 35-year-old was also a perfect six-for-six in save opportunities.

In the ninth inning of Saturday’s contest against the Guardians at Fenway Park, though, Jansen was clearly laboring on the mound. With a 6-5 lead to protect, the veteran right-hander gave up back-to-back singles to Myles Straw and Steven Kwan out of the gate.

That put runners at first and second with no outs. Jansen then fanned Amed Rosario, but followed by surrendering a game-tying RBI single to Jose Ramirez that pulled Cleveland back even with Boston at six runs apiece.

Jansen, who was charged with his first blown save of the year, remained in the game and got through the rest of the inning on 29 pitches (22 strikes), but not before getting checked up on by Red Sox manager Alex Cora and head athletic trainer Brandon Henry.

The meeting on the mound was brief, as Jansen assured both Cora and Henry that he was fine. After retiring Josh Bell for the final out of the inning, though, Jansen grimaced and looked rather uncomfortable as he made his way back to the home dugout.

When speaking with reporters (including MassLive.com’s Christopher Smith) following the Sox’ 8-7 walk-off win over the Guardians on Saturday night, Cora revealed that Jansen had dealing with back tightness throughout the day.

“His back got tight,” Cora said. “Before the game, he was running and he felt it. But he was available. He said, ‘You need me, we’ll go.'”

According to Jansen himself, he first felt his back tighten up during pregame conditioning and felt it again as he ran in from the bullpen in the top of the ninth. Though Jansen was able to pitch through the pain, he did receive some medication and is hopeful that it will kick in within the next “couple of days.”

Given what transpired on Saturday, Jansen will not be available out of the bullpen for Sunday’s series finale against the Guardians. The hope is that he will be back in action on Monday, when the Red Sox open a three-game set against the Blue Jays. If not Monday, then perhaps Tuesday.

“Pitching with lower-back tightness sucks,” Jansen told NESN’s Jahmai Webster. “We’ll see in a couple of days. We’ll take two days — probably a day or two — and then we’ll see how it feels and we’ll get back out there.”

Jansen’s blown save on Saturday represents the first for any Red Sox reliever this season. The righty now owns a 1.04 ERA with 12 strikeouts to 12 walks in his first nine outings (8 2/3 innings) with Boston. He is three saves away from 400 for his major-league career.