Detroit Tigers reliever reportedly has a torn UCL and will miss the remainder of the season.

CBS' Jon Heyman confirmed initial reports via Twitter on Thursday morning.

Nathan, 40, is in his second season with the Tigers and has made one appearance this season, earning a save on Apr. 6 by striking out one batter.

MLB's active saves leader (377) pitched in a rehab game on Wednesday with the Triple-A Toledo Mud Hens. The Tigers had placed him on the 15-day disabled list on Apr. 7 with a strained right elbow. 

Nathan threw 10 pitches on Wednesday before leaving the game due to injury.

"He felt a pop," Tigers manager Brad Ausmus told MLB.com on Wednesday. "He thought it was possibly scar tissue, tried to throw another pitch, but it didn't go so well."

Nathan made 62 appearances with the Tigers last season, going 5-4 with 35 saves. He posted a 4.81 earned-run average and a 1.534 WHIP.

A veteran of 15 MLB seasons, Nathan has made 777 career appearances with the Tigers, San Francisco Giants, Minnesota Twins and Texas Rangers. A six-time All-Star, he finished top-five in Cy Young Award voting in 2004 and 2006 as a Twin.

He has eclipsed the 40-save plateau on four occasions, most recently in 2013 with the Rangers. He signed a two-year deal with a club option with Detroit the following off-season. The Tigers' $10 million option kicks in for 2016, it includes a $1 million buyout.

Nathan has a 62-34 career record with a 2.89 ERA and a 1.118 WHIP. He has appeared in 10 career post-season games, going 0-2 with just one save.