"I am ready to move on to the next stage in my life and enter the NBA draft,'' the 6-foot-10 McGary said in a statement released by the school Friday. ''Being a part of a program that values integrity, it is important to let everyone know of a poor decision I recently made. I tested positive for marijuana during the NCAA tournament. We were notified of that result after the Final Four. I regret thoroughly disappointing my family, coaches and administration.''
McGary told Yahoo Sports he was facing a one-year suspension for the failed drug test.
McGary was terrific in the 2013 tournament as a freshman, helping Michigan reach the national title game, where the Wolverines lost to Louisville. He considered jumping to the NBA then, but instead came back for his sophomore year and was a preseason All-American.
But McGary played only eight games this season. He was bothered from the start by a back problem and eventually had surgery. He was shut down shortly after a Dec. 14 matchup with Arizona.
It was unclear how his future would be impacted by the injury. Was his draft stock still high enough for him to leave, or would he need to come back to Michigan in 2014-15? McGary is old for his class, turning 22 in June, but his injury made his decision a difficult one -- until the flunked drug test.
''I feel I'm ready, but this pushed it overboard,'' McGary told Yahoo.
McGary's departure leaves Michigan facing major personnel losses for a second consecutive season. The Wolverines lost guards Trey Burke and Tim Hardaway Jr. to the NBA after the 2012-13 Final Four run, but they won the Big Ten anyway this year behind Nik Stauskas, Caris LeVert and Glenn Robinson III. Michigan reached the NCAA quarterfinals before losing to Kentucky.
Now Stauskas, Robinson and McGary are all leaving early for the pros. The frontcourt looks particularly thin for next season, with Jon Horford transferring and McGary declaring for the draft.
The Wolverines will still have the rapidly improving LeVert in the backcourt, and both Derrick Walton Jr. and Zak Irvin return after contributing this season as freshmen.
McGary averaged only 7.8 points and 6.6 rebounds in his two-year career at Michigan, but his potential is tantalizing. In Michigan's six NCAA tournament games in 2013, he averaged 14.3 points and 10.7 rebounds.
Although he was injured most of this season, he remained a fan favorite and an energetic presence on the Michigan bench.
''Mitch has had a tremendous impact on our program from the moment he committed to us,'' Michigan head coach John Beilein said. ''The progress he has made on and off the court has been outstanding. His willingness to face a personal issue head on and his positive work ethic during his recent injury have helped him to grow in many ways.''