The school announced Monday that Stoglin, the ACC's leading scorer last season, was suspended for the year for violating the school's athlete code of conduct.
Mychal Parker, who had already announced that he was going to transfer, was also suspended for the year. Both would have been entering their junior seasons at Maryland in 2012-13.
The NBA confirmed that Stoglin's draft entry letter arrived at the league office by 10 p.m. ET on Sunday night, just two hours shy of the midnight deadline.
Maryland's staff was meeting Monday morning and wasn't available for comment.
"Being a University of Maryland student-athlete carries a tremendous honor and responsibility," Maryland athletic director Kevin Anderson said in a statement. "As much as we appreciate the effort these two young men gave to the program this season, they were unable to live up to that responsibility. We're disappointed, but hope they use this as a learning experience.''
Maryland finished 17-15 (6-10 ACC) in Mark Turgeon's first season in College Park, where he succeeded Gary Williams.
Stoglin averaged an ACC-best 21.6 points per game last season, while Parker averaged 4.3 points and 3.0 rebounds per game.
Stoglin figured to be the Terps' leader in 2012-13 as they tried to make an NCAA tournament run. With his departure, the Terps will lean heavily on big man Alex Len and wing Nick Faust, who are expected to be Maryland's most productive players. Maryland is still waiting to see if Pe'Shon Howard returns from a knee injury.
Maryland also brings back rotation player James Padgett and added a strong seven-player recruiting class, led by Sam Cassell Jr. (Baltimore/Notre Dame Prep), Shaquille Cleare (Houston/The Village School) and Seth Allen (Fredericksburg, Va./Fredericksburg Christian).
Michigan transfer Evan Smotrycz won't be eligible to play, but the Terps will need his leadership in practice.