Confirmation from @TheBadgerNation:
Danny O'Brien says that he's transferring because he's not going to get a chance to compete for the starting QB job in the fall #Badgers— Benjamin Worgull (@TheBadgerNation) June 10, 2013
As Jesse Temple (the reporter from Fox Sports Wisconsin who broke the story) points out, O'Brien has since deleted his Twitter account.
Early last month, O'Brien had a somewhat cryptic tweet that seemed optimistic, though his choice of images accompanying the tweet -- three, one of him fumbling and two others of him throwing the ball -- seemed puzzling. From our LinkShot of the May 2 tweet. (Ed.: The text of the tweet is now gone, as well, since the account's been deleted.)
A reminder of O'Brien's comments earlier this season against transferring, from the Wisconsin State's Journal write-up of today's news:
Near the end of last season, O'Brien said he was dedicated to returning this season and didn't want to transfer.
"I've gone through the transfer process once and that's hectic, (I) don't want to do that again, but we'll see," he said at the time.