Corey Kluber's injury woes show no signs of subsiding after the two-time Cy Young Award winner was ruled out for at least four weeks.

The Texas Rangers traded for three-time All-Star pitcher Kluber last December, sending outfielder Delino DeShields and pitching prospect Emmanuel Clase to the Cleveland Indians.

But the 2014 and 2017 American League Cy Young winner's belated Rangers debut did not go to plan.

Kluber, who missed most of 2019 with a fractured ulna bone in his right arm, lasted just one inning and 18 pitches against the Colorado Rockies on Sunday before leaving the game with tightness in his shoulder.

The right-hander was subsequently diagnosed with a Grade 2 tear of the teres major muscle in the back of his right shoulder.

Surgery is not planned, but Kluber faces a month out and, due to the truncated nature of the season amid the coronavirus pandemic, a 2020 return as a starter appears unlikely.

"The timeline is not on our side," Texas general manager Joe Daniels explained. "We will give him his period of rest.

"If the injury has progressed to the point where he can begin throwing, he'll do so with the potential to be possibly ready for the end of the season.

"If that is the case, it would be more likely as a reliever given the time needed to build up as a starter."

Daniels added: "It's a blow, there is no getting around it. We felt like he was in a really good spot. He had no physical issues at all. In talking to him today, he feels better than he has in years physically.

"There was no indication that this was coming. He was throwing the ball really well. We felt really good about him in the rotation."

But the Rangers, who hold a $18million option on Kluber for next year, are not necessarily giving up on the 34-year-old just yet.

"We acquired him with the mindset he could be here beyond this year," the manager said.

"This is obviously a physical setback but doesn't necessarily change our desire to have him back for next year. We need more information before we start talking about that."