Diagne was 5 of 8 from the floor and Warren Gillis added 14 points for Coastal Carolina (17-12, 10-5 Big South).
The Chanticleers led 17-4 with 12:32 remaining in the first half after Eric Smith's layup capped a 9-0 run. Presbyterian quickly responded with 12-straight points and cut the difference to five, 28-23, at the break. Early in the second half, however, Coastal Carolina held the Blue Hose to just two points in a 6-minute span, and led by 15 with 10:54 to play.
Rebounding proved crucial as the Chanticleers pulled down 12 more rebounds than the Blue Hose, 11 of those coming from the offensive end for second-chance points.
Markus Terry led Presbyterian (6-24, 2-13) with 16 points and William Truss added 15 rebounds.