No one has said when exactly Mario Manningham will return. However, he and Kendall Hunter both have been rehabilitating on a side field during practices. Hunter has been doing more -- cutting, pulling heavy chains, sprinting at full speed -- than Manningham, and Hunter still hasn't been cleared for practice. I realize their injuries are different - Hunter tore his Achilles' while Manningham had a torn ACL - and that could account for differences in their rehab routines. But it still seems as if Manningham has a few more steps to go before he can get back on the field.
As for stealing the No. 2 role ... Remember, Manningham never was the no. 2 receiver in New York. He came in on third downs, which was similar to his role with the 49ers last year. I'm not sure the 49ers see him (or Kyle Williams, for that matter) as an every-down type player. They are small guys, and their injuries last year only reinforce the concern that they can't withstand every-down pounding for 16 or more games. It's another reason to expect some sort of rotation at the position during the season.
Hunter figures to be the primary backup to Frank Gore once he gets healthy. Manningham will be in the mix for snaps at WR2 when he makes his return. The team recently signed Austin Collie to compete for snaps as well.