Now, it appears he won't be able to.
Kimbrel was unavailable Friday night in the ninth inning of a 6-5 victory over the Tampa Bay Rays at Fenway Park after tweaking his left knee during pregame warmups, according to Red Sox manager John Farrell.
Kimbrel underwent an MRI exam, the results of which will be available to the team on Saturday.
"Everything that we did early, he was fine," Farrell said after Koji Uehara allowed a solo home run but still picked up the save in Kimbrel's absence. "But then he felt something while the running was taking place, unfortunately, during [batting practice] while he was shagging."
Kimbrel, who has a 3.55 ERA and 17 saves in 34 appearances, was among six Red Sox players named to the American League All-Star team. Asked if Kimbrel would still be able to pitch Tuesday night in San Diego, Farrell said, "I would venture to say he's not going to be available for that."
In addition to Kimbrel, reliever Junichi Tazawa was unavailable Friday night due to discomfort in his right shoulder. Tazawa hasn't pitched since last Sunday against the Los Angeles Angels, although Farrell said the Red Sox have not yet felt the need to order an MRI exam.
Also, left fielder Brock Holt left Friday night's game with a Grade 1 sprain of his left ankle after sliding awkwardly into second base in the fourth inning. Holt was in a walking boot after the game, a "precautionary" measure, according to Farrell, and will be reevaluated Saturday. With the Red Sox facing a left-hander (Tampa Bay's Matt Moore), it was likely Bryce Brentz would have gotten the start in left field anyway.
And to complete the Red Sox's injury list, first baseman Hanley Ramirez departed in the ninth inning after fouling a pitch off his left shin. Ramirez said he doesn't expect to miss any time.
"The way I feel, hell no," he said. "Just come in early and see how it feels and go from there."