Per Tribe Insider, Kluber was diagnosed with a strain of an internal oblique after leaving Sunday's rehab start with Triple-A Columbus following the first inning. He will be reexamined in two weeks to determine his readiness to resume a throwing program.
The 2019 season couldn't have started much worse for the two-time American League Cy Young Award winner. Through seven starts, he had a 5.80 ERA and averaged 3.8 walks per nine innings, up from a American League-best 1.4 in 2018, per Baseball Reference.
Compounding matters, Kluber suffered a non-displaced fracture in his right forearm after getting hit by a line drive off the bat of Miami Marlins right fielder Brian Anderson on May 1.
The Indians did little to improve their roster in the offseason, counting on the health and performance of their biggest stars to carry them back to the playoffs. That plan has unraveled completely as Kluber, Francisco Lindor and Mike Clevinger have all missed time.
The injuries to Kluber and Clevinger have hit Cleveland particularly hard as the team is leaning heavily on the starting rotation to secure a fourth straight American League Central title.
The Indians head into Tuesday just two games behind the Twins for first place in the division. Not having Kluber back at this stage does hurt, but they've managed to get back into playoff contention thanks to Clevinger and Shane Bieber stabilizing the top of the rotation.