Painter signed a one-year deal to come to the Giants before the 2013 season.
This is simply an insurance move for the Giants just in case Ryan Nassib craps out. Painter is not a great backup by any means, but should Nassib fail to progress, the club needs some assurance they have someone competent.
Why not David Carr, you ask? No idea. He's without a job these days and it's baffling why the Giants keep choosing Painter over Carr.