how can the offense NOT take a step back?

Come on bro! Spiller isn't even close to the mismatch nightmare Jimmy Graham is. You lost me with that comment. Spiller is an explosive cat, but he hasn't been used in the Bush/Sproles role before (really). To say he's "every bit" the mismatch Graham is sounds just plain ignant.

All right. I was giving your OP some slack, but you're placing a lot of of your argument on the loss of Graham while mentioning not having the Sproles factor. We were number one last year with Graham and without Sproles. Now we have no Graham or Thomas but added Spilller, and beefed up the Oline. We won't get the production from the TE like we did with Graham, but will be solid and production will come from other areas. We won't have the "Graham" mismatch, but we have a bigger variety of mismatches spread across Cooks, Spiller, Ingram and Colston. If a young receiver or two step up, that's lagniappe. If Brees stays upright, not worried about offensive production tapering off.