Achilles is a major issue. You don't want to mess with them. Injury to the achilles can be much more serious than your standard hamstring or even knee. I like Yak and it is my hope that this isn't a career ender.
Depending on the severity, it is possible that he may never make it completely back. There was an all-pro cornerback, Kevin Smith, for the Dallas Cowbows that ruptured his achilles. Even with the all the therapy, desire, and money he was never again was the player that he had been. The corner position depends on speed so maybe there is a difference. Yak isn't a pace player so maybe it won't be an issue for him. Then again, it might.
This injury is a such a buzz kill.