All he missed on his sick day was the third-biggest rout in NCAA tournament history, a 103-47 win over No. 16 seed Chattanooga in Philadelphia in yesterday's opening round.
Calhoun was admitted to the Hospital of the University of Pennsylvania yesterday afternoon for tests and was to be kept overnight for observation.
An unnamed source told ESPN.com that Calhoun, 66, was treated for dehydration and received IV fluids at the hospital. The school did not say what was wrong with the coach.
In a statement released by UConn, Calhoun said he will be re-evaluated this morning and hopes to be released then.
The Huskies hope the Hall of Famer will be back healthy and revitalized for the second round, and possibly beyond.
Associate head coach George Blaney said Calhoun called him at 11:45 a.m. and told him he felt "under the weather."
Calhoun missed time in January 2008 with what the team called a combination of stress and exhaustion.
Calhoun has missed 21 games in his Hall of Fame career, including one other game this season - a Jan. 3 contest against Rutgers.
Blaney said Calhoun spoke with the team via speakerphone after the game, telling the players he expected to be back with the team very shortly.
North Carolina:: Forward Tyler Hansbrough broke the Atlantic Coast Conference's career scoring record. The 6-foot-9 senior needed three points in his team's NCAA tournament opener against Radford in Greensboro to pass Duke's J.J. Redick for the mark. Hansbrough finished with 22 points in the top-seeded Tar Heels' 101-58 win over No. 16 seed Radford, giving him 2,789 for his career.
Dayton:: Coach Brian Gregory, on the eve of the team's first-round game against West Virginia, said he has agreed to a five-year contract extension to stay with the Flyers through the 2017-18 season.