Talent upgrades/downgrades by situation
 

Red zone/jumbo offense

Gronkowksi could be an immediate upgrade over Watson.
Hernandez could be an immediate upgrade over any WR or TE not named Moss or Watson.
In a longer shot, Tate or Price could be an immediate asset.
Everybody else is the same (Vollmer perhaps excepted).
But there were plenty of plays when Welker contributed in the red zone, so not having a great small-slot-receiver option is a loss.

Red zone/jumbo defense

We're hoping Spikes will be a big asset.
We've added a couple of vet DTs, and last year's rookies are older, so the long line of DTs in jumbo defense might be improved.
Everybody else is pretty much the same, unless Cunningham helps.

Nickel/dime offense
We've lost ground until Welker comes back; he outweighs everything.
We've probably added enough talent, however, to at least offset his rust once he's back.

Nickel/dime defense
McCourty should be an asset immediately.
Meriweather is still improving.
Butler should make a sophomore jump.
The Ws could still improve.
Other than that, we're basically waiting for Chung/Cunningham/Crable/et al. to develop (and new-guy-in-system Burgess).