Report: Rays RHP Alex Cobb has partial ligament tear

Tampa Bay Rays starter Alex Cobb had a new MRI that revealed a partially torn elbow ligament, according to Marc Topkin of the Tampa Bay Times:

Informed speculation on #Rays Cobb: Partial tear in elbow ligament showed in new MRI, thus wait and see how he responds to rest, treatment

— Marc Topkin (@TBTimes_Rays) May 5, 2015

Cobb has been on the disabled list all season with forearm tendinitis and Topkin reported he was back to throwing off a mound before suffering a setback yesterday and being shut down:

#Rays Cobb had "a little bit of a setback," will be shut down from throwing and see doctor, Cash said. "He didn't feel as good as he hoped."

— Marc Topkin (@TBTimes_Rays) May 4, 2015

What does this mean for the Rays rotation?

If Cobb misses an extended period of time, it would mean right-handers Nate Karns and Alex Colome stay in the rotation.

Karns has made six starts as Cobb's direct replacement in the rotation, with a 4.05 ERA and 1.14 WHIP in 33⅓ innings with 17 walks and 29 strikeouts. Karns had pitched just 24 innings in the majors prior to this season, a dozen last year with the Rays and another 12 in 2013 with Washington.

Colome missed nearly the first month of the season with an unspecified illness, but returned to the Rays rotation Friday, pitching five shutout innings against Baltimore, allowing three hits and striking out six. He had a 2.66 ERA and 1.23 WHIP in a 23⅔ inning cameo last season.

What do the Rays miss with Cobb out?

Cobb was Tampa Bay's best starter in 2014, posting a 2.87 ERA and 1.14 WHIP in 166⅓ innings last year over 27 starts. He walked 47 and struck out 149 with an ERA+ of 130.

Last season was Cobb's second straight with a sub-3.00 ERA, as he had a 2.76 ERA in 143⅓ innings in 2013.

Update: Cobb will try to pitch through the partial ligament tear, according to Igor Mello of CBS Sports.