With Crabtree out for most of the season, someone on the team has to step up, even if Baalke decides to sign someone from the remaining free agents. To get a clear picture of the in-house options, I looked at the target distribution in the 10 games Kap started, and the game against the Rams after he took over. Data is from ESPN Box scores and play-by-play log (for the STL and ARI game when Alex also played) .The following table has the passing stats broken down by targets for all the pass attempts that were not called back for penalties.
Surprisingly, Kaepernick's #2 target was Randy Moss, although he barely caught half of the passes thrown to him, and both Davis and Walker got more yards from less pass attempts. With Moss and Delanie gone, and Crabtree out, Kaepernick has only one if his top-4 targets still on the team.
The team, however, is getting two WRs back from injury, Williams and Manningham. How important were they in the passing game when they played? For the games vs. STL(x2), CHI and NO, the stats are broken down in the table below. I also listed the contribution of each receiver to the team totals. Running backs are lumped together.
So, they were very important. MM and KW together accounted for 26.9% of the targets and 32.1% of the total reception yardage, which would account for most of the loss due to Crabtree's injury - 34.2% of targets and 35.6% of yardage in the Kaepernick era. The biggest surprise is that Manningham was the best receiver on the team, even if someone else had more yards in each of the four games. Unfortunately, he missed two games for injury, and came back against Seattle only to have his knee busted. Williams were reliable in the whole season to catch two passes out of three targets. When they were injured, the less reliable Moss and Walker had to catch those passes.
So Manningham has already demonstrated that he can be #2 WR on the team. More importantly, Kap trusted him on the field. Unfortunately, he probably starts the season on the PUP list, and won't be back until week 10.