Mankins might not be a plus pass protector, but Devey's third quarter in Miami was the worst thing I've ever seen on a Pats o-line.
Vollmer got rolled up on in the 3rd quarter, similar to what put him on IR last year, and Fleming subbed for him. He came back in because you can't feed a rookie RT to Cameron Wake, and that's when Wake went berserk. Until that point Vollmer was probably the Pats' best lineman.
The Pats offense went in the toilet in Miami because Wendell and Vollmer both got injured in the 3rd quarter, meaning the Pats had to ride out Devey's meltdown and couldn't give Solder the help he needed because Vollmer was walking wounded. If Mankins is active in place of Devey the Pats have a chance because you can chip to help your OTs so long as nobody's barreling through the B gaps consistently. As in, every play.
The trade of Mankins was a significant factor in the loss. The offense stays on the field longer with him, perhaps scores a few more points, but most importantly doesn't leave the defense on the field to die.
That said I was and am a big fan of the trade because playoff games are won in January not September, and I think Wright + random guard will be better for us then than Mankins + nobody, who was the player at Wright's position in camp.
It did hurt us in September though.