With Aaron Ramsey out for around a month with a hamstring issue, and Mikel Arteta and others still unavailable, Arsenal are running low on midfielders (along with plenty of other things). It appears that Arsene Wenger doesn't deem any of the youth midfielders we saw at midweek ready for the big show, because he's resorted to drastic measures.
Francis Coquelin hasn't been all that impressive for a while, which is why he's on loan at a Championship club. But he is at the very least Premier League-experienced, and he's played relatively competently for Arsenal in the past. If he has to play tomorrow he has a level of familiarity with the team that wouldn't make him look totally lost, which in an emergency I guess is all you can really ask.
Tomorrow should be...interesting.