Albeck, 70, was talking to Raptors center Eric Montross just before his team took the court when he slumped over in a chair. He was carried off on a stretcher and taken to St. Michael's Hospital, where he is undergoing tests.
"Stan is being evaluated," Toronto coach Lenny Wilkens said. "I haven't heard anything else."
"It is a tough situation when you know you have a game to play, but you want to be around to give your support," said Raptors superstar Vince Carter.
A former head coach with Cleveland, San Antonio, New Jersey and Chicago, Albeck has served as an assistant under Wilkens for the past six seasons, including two with Toronto. His most successful stint came with the Spurs, who won division titles in each of his three seasons.
Albeck owns a 307-265 NBA coaching record and a 209-117 mark at the college level, where he spent 14 seasons with Adrian College, Northern Michigan, Denver and his alma mater, Bradley.
Before becoming an NBA head coach, he served as an assistant for nine seasons in the NBA and ABA, working under the likes of Jerry West, Hubie Brown, Wilt Chamberlain, K.C. Jones and Alex Hannum.