Stats listed in order of importance. I'm not even touching pass blocking. Way too many variables. Cleveland and Buffalo basically overhauled their entire rushing attack. Obviously, adding Joe Thomas and Jamal Lewis helps. Davis entered into the position with the most personnel consistency. The benefits of signing Steve Hutchinson occurred immediately. Davis and Steinbach were both signed primarily for their pass blocking. Davis has allowed less than one sack for the season.
It would seem to be the free agency rule of thumb: Free agency is only a worthwhile way to acquire talent when A) It's elite talent, or B) You're one player away. Doesn't matter if that player is a guard, safety or left tackle. No more complicated than that, folks.