George Blaney, the team's associate head coach, will lead the team in Calhoun's absence. The Huskies (14-7, 4-5 Big East) have lost four games in a row. They host Seton Hall on Saturday before travelling to Louisville Monday.
The school confirmed that Calhoun will miss at least those two games.
"Jim has been able to manage it with the physical therapy and stretching, but over the last several days, things have become worse and he is not able to deal with this on a day to day basis, so other options need to be considered," Schulman said. "Right now, he is physically unable to coach."
Calhoun has had a history of health problems. He is a three-time cancer survivor, overcoming prostate cancer in 2003 and skin cancer twice, most recently in 2008.
He has missed 21 games during his career at UConn, 17 for medical reasons. He has had to leave another 11 games with health problems. His last extended medical leave came in 2010, when he missed seven games with stress-related issues.
Calhoun is No. 6 on the all-time wins list with 867. He has won three national championships at Connecticut and was inducted into the Basketball Hall of Fame in 2005. He coached the team to its fourth Final Four and third national title last April.
The subject of Calhoun's tenure is not new. He said last month he decided to not retire after last year's national championship in large part because he wanted to see through the NCAA sanctions leveled on him and his program for recruiting violations. The NCAA required Calhoun to sit out wins over South Florida and St. John's and a loss to Seton Hall for violations that included a finding that the coach had failed to maintain "an atmosphere of compliance" in the program.
He told reporters that the idea of bringing closure to that issue was a "major, major factor" in his decision to come back this season.
In August, Calhoun said through the assistant director of athletics that he informed university President Susan Herbst he would coach during the coming season.
In June, he said he felt good, worked out and spent a lot of time riding his bike. Each year, he rides between 25 and 50 miles at his annual Jim Calhoun Cancer Challenge Ride and Walk. In 2009, he broke several ribs and was hospitalized after falling during the charity event.