'We appreciate his competitive efforts and also appreciate the first-class manner in which he has handled himself,' said Detroit assistant general manager Al Avila.
Mickelson threw batting practice for 30 minutes on Friday in front of Mud Hens' manager Larry Parrish and pitching coach Jeff Jones. The plan was that if both were impressed, and the Tigers signed off on it, Mickelson would be offered a short-term contract to pitch in a game either Sunday or early next week.
'I am certainly disappointed but I completely understand and respect the decision,' said Mickelson. 'If I can get my velocity up, we may revisit this in the future.'
Mickelson apparently had good movement on some of his pitches, but never hit 70 miles per hour during Friday's tryout.
'Throwing a baseball is an important part of my workout program, so if I can get my speed to 85 miles per hour or above consistently, I wouldn't rule out trying this again in the future,' said Mickelson. 'That would be the benchmark.'