I actually don't think Sanu is as untalented as many make him out to be. He is a tough runner after the catch, smart and has strong hands (though he had some concentration drops in 2014). There was a reason why he got over $30M in FA and had teams like the Patriots very interested in him as well.
But I agree with pwingles that WR2 in Atlanta (and specifically with OC Shanahan) is not an attractive target for fantasy. Hard to see him getting more than 100 targets (probably even less than that) and Sanu's a possession guy, so he's not going to do a whole lot of fantasy damage with 5-6 targets per game. The FBG staff all have him in the 55-60 catch, 650-700 yards receiving range. Seems reasonable to me and those type of numbers aren't of much use for fantasy.
We don't talk about handcuffs for WRs, but that may be where there is a little bit of weekly upside with Sanu. He had some big games in 2014 when AJ Green was out and would be a startable option if Julio missed games, which isn't an uncommon occurrence.