ST. LOUIS -- Cardinals reliever Tyler Johnson will undergo arthroscopic surgery on his left shoulder, general manager John Mozeliak confirmed on Tuesday. Dr. Neal Elattrache will perform the procedure on Wednesday in Los Angeles.

Johnson tried for more than two months to address his shoulder trouble non-surgically, and got as far as throwing off a mound. However, the rehab didn't progress as well as he or the team hoped, so he will have an operation.

"It's just not responding," Mozeliak said on Tuesday afternoon.

Johnson first encountered trouble early in Spring Training. He was diagnosed with tendinitis and a rotator cuff strain in his throwing shoulder, and was shut down. More recently, the club has called Johnson's condition shoulder capsulitis.

After extensive rest, Johnson began a throwing program. However, after re-evaluation by doctors, including Dr. Elattrache, the decision was made for Johnson to undergo surgery.