The Tigers placed southpaw Dontrelle Willis and right-hander Joel Zumaya on the 15-day disabled list on Sunday and returned left-hander Kyle Bloom to the Pirates.

Willis, a former 22-game winner, was placed on the DL due to an anxiety disorder.

Willis said the diagnosis came after follow-up blood tests showed something of concern. Doctors told him that the condition is treatable and that they'll start him on a regimen.

"This is not depression," Willis said. "This is something totally different. This is something where they saw something in my blood that they didn't like. "I'm not crazy, though my teammates might think that I'm crazy."

He went 0-2 with a 9.38 ERA in eight appearances with the Tigers last season following his blockbuster trade to the Tigers the previous offseason. Despite making adjustments to his delivery, the southpaw continued to struggle this spring. Willis allowed 15 runs (12 earned), 17 hits and seven walks in 8 2/3 Grapefruit League innings.

Zumaya's DL assignment was due to a sore right shoulder, and it is retroactive to March 27. The hard-throwing reliever has tossed just one inning this spring after being limited to 21 appearances during an injury-plagued 2008 season.

Bloom was selected from the Pirates in the 2008 Rule 5 Draft. He allowed six runs (five earned) in 5 1/3 innings this spring.

With Sunday's moves, the Tigers have 35 players remaining in their Major League camp.