Santana is due to undergo surgery Tuesday for a torn anterior capsule in his pitching shoulder and will be lost for the season.
Francisco is having a slow return from December surgery to remove a bone spur from his right elbow.
Marcum is expected to be activated for Game 6 of the season, after dealing with shoulder and neck discomfort. He officially was listed on the DL with biceps tendinitis, which had not previously been mentioned by the club.
Mejia has experienced forearm tendinitis.