George Allen was fired after 2 preseason games in 1978
Jack Patera was only two games into his seventh year with the Seahawks in 1982
Joe Collier only made it two games into the 1968 (AFL) season before the Bills fired him.
Hugo Bezdek was fired by the Rams after just three games into the 1938 season
I don't think it is out of the realm of possibility that losing to the Giants will be the last of Matt Rhule in Carolina