I seriously think Gallas is better playing centre than left. While Djorou is too inexperienced and does not have the muscle to outmuscle bigger strikers. Flamini is good for the leftback spot which he filled in well, and I think he plays better than Cole in Leftback. Defensively he is better but Cole is more attack-minded.
But lets not forget the emergence of Cole was because of Henry and Pires (then) drifting on the left.