The No. 26 overall pick in this year's draft, Windler has yet to play for Cleveland after suffering a stress reaction in his lower left leg during workouts just prior to training camp. He recently played for the Canton Charge but began experiencing symptoms and was shut down.
The Cavs said an MRI confirmed the previous diagnosis, and Windler will be out for at least two weeks to undergo more treatment and rehabilitation.
Windler will also get a second opinion from an orthopedist in Indianapolis.
In his first game for the Charge, Cleveland's G League affiliate, the 6-foot-8 swingman scored eight points and had four rebounds in 17 minutes last week.
The Cavs said Windler's status will be "updated as appropriate."
Cleveland will continue a three-game trip in Milwaukee on Saturday. The Cavs snapped an eight-game losing streak with an overtime win at San Antonio on Thursday.