Cal called the former hooper his "brother" in an emotional tweet ... and added, "I know how much Reggie meant to Kentucky & how he inspired others."

"Reggie and I worked together at Pitt in the 80s and have remained friends," the Wildcats head coach said. "I'm going to miss my brother, may God bless you Reggie."

No cause of death has been revealed ... though the Kentucky icon battled various health issues in the waning years of his life -- requiring several transplants.

He was 67 years old.

Warford played at Kentucky from 1972-1976 and was the program's second-ever Black player. Tom Payne, who signed with the Wildcats in 1969, was the first.

Over the course of his four-year career, Warford played in 50 total games -- scoring 206 points.

Warford went on to graduate from UK with a degree in arts and sciences ... making him, at the time, the first Black four-year player to accomplish the feat.

Kentucky officials remembered the college standout on Thursday while emphasizing the "important role" he played in the landscape of Wildcat sports history.

"It is with great sadness we share the passing of Reggie Warford," the school said in a statement. "Our deepest sympathies go out to his family, friends and teammates."

"Warford was an NIT Champion and the first Black men's basketball player to graduate from the University of Kentucky."

Reggie is survived by his wife, Marisa, and sons, Grant and Tyler.