Seth Lundy's 18 points and John Harrar's fifth double-double of the season were not enough to beat the Spartans.
Diaz has 24 years of collegiate coaching experience and was most recently Miami's head coach.
Wisconsin entered the game with a seven-game winless streak.
Officials said crew members climbed to the building's roof and found only one of the Computer Building's air ventilation units was functioning fully.
"I could not pass up the chance to be with this family and play the game I love again."
$5 of every ticket will be donated to support THON 2022's fundraising campaign.