Not entirely sure on the rules, Elneny played in the europa cup this season. which I believe makes him cup tied... so that isn't entirely on Wenger except his reluctance to find a player in that role we desperately needed in summer that everyone but him realised.
It was simply ridiculous to sub Coquelin full stop. Wenger never seems to look at the pitch and sub whoever on the pitch is performing the worst, which at that stage of the game would probably be sanchez or Ozil. Sanchez having been poor for so many games in a row I would have taken him off for Campbell, or even Gibbs if he wanted to push him into the middle and Ozil out wide.
Coquelin's biggest improvement over Arteta/Flamini was not making the rash stupid tackles in our defensive half.... so in the game where not being reckless is so important he takes off Coquelin, brings on a significantly worse player who proceeds to do something predictably reckless.
Why did the entire clubs fan base, 99% of pundits and just about every fan at every other club all think buying a quality defensive midfielder this summer was crucial.... because Arteta is both rubbish and unreliable fitness wise, and Flamini is rubbish and also unreliable fitness wise.
Coquelin having never played a long season was a HUGE risk to presume he could play uninjured and stupid to not have quality back up. Flamini and Arteta shouldn't have been brought to the club for the roles they were given, Flamini was an improvement on Arteta.... but still not actually good enough. Arteta was never a defensive midfielder.
If we brought someone quality, even if it was Elneny, in summer, Coquelin could have been rotated, Elneny(or another player) would have had more time to gel with the team before an important game like today and he wouldn't have been cup-tied.