Former NBA star Mark Aguirre was hospitalized on Wednesday after collapsing in a fitness center near Plano, Texas, according to the Dallas Morning News.
The 51-year-old reportedly became ill while running on a treadmill and fell off.
He was said to have lost consciousness and is now in the critical care unit.
"There was no heart attack," said Frank Zaccanelli, former Mavericks general manager. "What it was, it was a clogged vessel -- not artery, vessel -- and while he was working out, it just caused him to black out. There was no cardiac arrest. There was nothing. He fell."
Aguirre played seven and a half seasons with the Mavericks before getting traded to the Detroit Pistons, where he won two NBA championships.