ShunQuez Stephens had 10 rebounds and Fred Miller had seven assists as Upstate (16-12, 9-6 Atlantic Sun) used a 15-6 run to take a 64-44 lead with 2:02 left.
The Spartans opened the second half by extending a 27-24 halftime lead to 40-28. Craig capped the run by scoring back-to-back on a 3-pointer and layup.
Willie Green was Stetson's lone player in double figures with 11 points. The Hatters (7-19, 5-9) shot just 2 of 15 from 3-point range.
After the Hatters fell behind early in the second, they played even with Upstate for the next 7 minutes.
The Spartans then broke the game open on Mario Blessing's 3-pointer with 7:25 to go which sparked the late run that put the game out of reach.