I think that Sagna was only good player. Vermaelen and usually pretty solid Monreal were both really poor. Mistake from Wenger really though as he could have countered Martinez with a single move to back three and moving Monreal up the field, but it's easy to say now. Everton still were better in every possible way.
Cazorla played quite well, but Vermaelen kept being dragged out of position by Naismith's clever positioning and his own impetuousness, while Monreal had to deal with Romelu Lukaku, a matchup that isn't entirely fair.
Wenger hasn't played a back three in... maybe ever. Like I said, he's a bit tactically inflexible. Martinez exposed that.
but he has still been below par for most of the campaign. If he really wants to go in summer won't mind it if we get solid replacement.
He has been below par, albeit not for that match which was the point. I do wonder who you could get as a replacement. If he goes and you don't get fourth then you're going to be in trouble.