I seem to remember a few games where Baldwin was catching several passes and Tate not being visible. Just as someone noted above, it probably is based on how the defense is rotating their coverage. In the AZ game, seemed like Wilson was trying to hit Kearse a whole lot more prior to him munging up his ankle.
The WR corp needs a healthy Harvin and Rice, or similar type talent to get to the next level. They are not a group currently that strikes fear in an opposing team's defense. They are effective but not dynamic. The team's 3rd WR on Sunday was Ricardo Lockette with Bryan Walters backing up all 3 spots. Tate, Baldwin, Lockette and Walters. I think an NFL defense can shut the majority of these guys down with the addition of a DL that has 3 major talents on it.
This is all the team has. If Baldwin is having a down time, he will be trying to pick it up. If you see the lack of production, he and the coaches see it as well.