Per an email from an OSU spokesman, Crowell will not be cleared by team doctors to play in future seasons, while O'Connor has requested a transfer closer to home.
The decisions increase the possible number of spots open as the Buckeyes attempt to fill the rest of this year's recruiting class.
Crowell hails from Waldorf (Md.) North Point and actually began this season as the team's No. 2 middle linebacker. He finished the campaign with one tackle in three games.
However, he has fought injuries for much of his career. A three-star prospect coming out of high school, he suffered a leg injury late in his senior season that was so bad it kept him out of the entire 2011 campaign at OSU.
He later told BSB that was probably the hardest year of his life.
"It was just tough watching everybody else compete and go through the grind, and you're just sitting back and watching," Crowell said on Media Day this August.
He worked as the team's No. 2 linebacker through fall camp and even saw time when the linebacking unit was banged up in the UAB contest, but Crowell did not play in the second half of the season.
O'Connor was a three-star prospect picked up by Urban Meyer late in last year's recruiting class. The offensive guard originally committed to Penn State but switched his pledge after the Jerry Sandusky scandal resulted in longtime PSU head coach Joe Paterno being let go.
However, the Windsor, Colo., native did not play this year after undergoing microfracture surgery on his knee early in fall camp. He was expected to play either guard or center for the Buckeyes.