Blackshear was assessed a flagrant foul 2 and was ejected just 90 seconds into the second half of the Charleston Classic opener in South Carolina.
The Virginia Tech transfer played only five minutes Thursday after picking up two first-half fouls, finishing with one point, two rebounds and three assists. He entered the game as Florida's leading scorer and rebounder, averaging 14.5 points and 11.0 rebounds through four games.
Blackshear, a 6-foot-10 power forward from Orlando, was the most sought-after graduate transfer on the board last spring. After removing his name from the NBA draft, he ultimately chose Florida over Kentucky and Tennessee, as well as a potential return to Virginia Tech.
Florida led St. Joe's by 16 at the time of Blackshear's ejection, but the Hawks cut the lead to two points in the final minute before Florida hung on for a 70-62 win.
The Gators (3-2) will play Miami in the semifinals of the Charleston Classic on Friday at noon.