While it doesn't appear to be anything serious...not sure if this is the start that JonasMania needed.

With training camp still a week away, prized Raptors prospect Jonas Valanciunas has injured his left foot. While the team said a full update likely wouldn't be coming until Monday, Valanciunas does not appear to be seriously injured, though he was photographed in a walking boot outside the ACC this weekend. Valanciunas, like most basketball players, has had minor ankle issues in the past and walking boots are known to speed up recovery from minor sprains and strains

Here is a picture of Jonas in the boot, but also the blogger from the score notes at the end that because of the type of boot and no crutches indicates it is not serious. http://blogs.thescore.com/raptorblog/2012/09/23/valanciunas-in-walking-boot/