The 49ers have signed QB J.T. O’Sullivan to a 1-year contract.  O’Sullivan played for new offensive co-ordinator Mike Martz last season in Detroit and that’s a big reason why he will battle for the #3 job on the Niners behind Alex Smith and Shaun Hill.  O’Sullivan played in 5 games last season for the Lions and he completed 13 of 26 passes (50%) for 148 yards with 1 TD pass and 2 interceptions (48.2 QB Rating).  This was a nice low risk signing for the Niners as O’Sullivan knows Martz’ offense.