The bottom line: Edwards was not contributing much. Injuries were one factor. They might not have been the only factor, though it's unlikely Harbaugh will go into specifics if he thought Edwards did not fit.
Edwards has 15 receptions for 181 yards and no touchdowns in nine games, with five starts. He missed time to knee surgery earlier in the season. Shoulder trouble also seemed to slow him at times. He missed no games with the New York Jets in 2010.
Edwards and Josh Morgan started the 49ers' regular-season opener against Seattle. Edwards' release and Morgan's placement on injured reserve reflect significantly different dynamics at the position. The team will presumably have Ted Ginn Jr. and Kyle Williams back from injuries for the playoffs, if not sooner. Their presence, coupled with Michael Crabtree's improved play, would restore some depth to the position.
But the offensive mix is changing. Delanie Walker's jaw injury will lead to more playing time for veteran tight end Justin Peelle. We could see the 49ers use two running backs more frequently. We could see a few more three-receiver looks if Ginn and Williams are healthy enough to contribute.
Bringing in a big-name veteran for the playoffs wouldn't make a great deal of sense, in my view. The 49ers are not going to become a pass-happy team. They care about locker room dynamics. Harbaugh prefers heavier personnel groupings anyway. Crabtree is playing well enough to serve as the primary option at wideout. Vernon Davis has become more involved. The team probably needs another tight end as much as it needs another wideout, in my view.