Nick Piecoro of the Arizona Republic reported the news, noting general manager Mike Hazen said he hopes the southpaw is out for just a couple of starts.
The 31-year-old is in his first season with the Diamondbacks after signing a five-year, $85 million deal in the offseason.
He has struggled in limited action, though, tallying a 9.35 ERA, 1.56 WHIP and 13 strikeouts in 17.1 innings.
Bumgarner is obviously best known for his time with the San Francisco Giants, spending parts of 11 seasons with the squad while helping it take home three World Series titles.
Though he's especially shined in the postseason during his career, he's been an elite starter in the regular season as well with four All-Star appearances and Cy Young votes in five different seasons. The question has been whether he can regain this level of production after a career-worst 3.90 ERA in 2019.
The latest injury could prevent him from reaching expectations and turning things around, especially if he is forced to miss an extended stretch.
Arizona has talented young pitchers ready to step up in the rotation, but the lack of experience behind Robbie Ray could create question marks going forward.