Miles, who started 12 games last season, completed 66.6% of passes for 2,397 yards, 17 touchdowns and four interceptions.
Petersen said Miles' leave of absence is not for disciplinary reasons.
“Cyler is dealing with some things in his life that are more important than football, and he felt it was important to take some time away from the game,” Petersen said. “We are working to support him in any way we can and hope he returns back to the football field soon.”
Miles was suspended for spring practices last year and was also suspended for the first game of the 2014 season.
Washington finished 8-6 and lost in the Cactus Bowl to Oklahoma State.
- Paul Palladino