Tucson, AZ -- (Sports Network) - Lute Olson's doctor held a news conference on Tuesday and said the former Arizona coach suffered a stroke and was advised to retire.

Dr. Steven Knope said Olson had a stroke in the front part of his brain, which caused severe depression and changes in judgment. Knope said the stroke was confirmed after Olson underwent an MRI because the former head coach did not respond to treatment for depression.

Knope said based on the MRI and other exams, it's believed Olson suffered the stroke within the past year.

"I can't tell you how disappointed he is that he can't be here," Knope said. "He is frankly devastated and this is something that is simply beyond his control. This is not an issue of character strength or weakness or someone who just couldn't muster the strength to do one more season."

It was last Thursday when Olson announced his retirement as head coach of the Wildcats. Russ Pennell was named interim men's basketball coach a day later.

The announcement last week ended the 74-year-old Olson's 25-year reign at the helm of the Wildcats. He compiled a 780-280 career record at Arizona, Iowa, and Long Beach State. His 589-187 record with the Wildcats includes the 1997 national championship, four Final Four appearances, 11 Pac-10 titles, and 20 consecutive 20-win seasons. Olson has also won seven Pac-10 Coach of the Year awards.

His 27 NCAA Tournament appearances as a coach are one behind Bob Knight for the all-time record, and Olson entered the season second behind Duke's Mike Krzyzewski for most wins among active NCAA Division I men's coaches. Inducted into the Basketball Hall of Fame in 2002, Olson also guided Iowa to the 1980 Final Four.

The Wildcats are coming off a disappointing campaign in Olson's absence in which they went 19-15, 8-10 in the Pac-10, with former Olson assistant Kevin O'Neill at the helm. Arizona finished in seventh place in the Pac-10 -- its worst finish since 1982-83, the season before Olson started at Arizona -- but still ran its streak of consecutive NCAA Tournament berths to 24.

Arizona was eliminated in the first round by West Virginia.

Olson made it very clear earlier this year that he was intent on returning to the sideline for Arizona despite missing last season to deal with personal issues. When Olson took the leave of absence last November he did say that there were medical concerns as well.

The Wildcats open this season on November 17 against Florida Atlantic.