This injury comes at a trying time for manager Arsene Wenger.
He is coming under increasing scrutiny for a lack of top-class signings this summer, and while much of the talk has focused on a prolific striker to replace Robin van Persie, Arteta's injury highlights Arsenal's serious lack of depth at defensive midfield.
With official word via The Telegraph of Etienne Capoue's transfer to Tottenham Hotspur along with reports from The Metro and others that Luiz Gustavo may sign with VfL Wolfsburg, the frustration with Wenger's seeming indecision this summer will surely grow.
As an organization, Arsenal seems to realize this, with Arsene Wenger himself going on record courtesy of Arsenal.com:
There are 18 days to go, so that is a long time in the transfer market and we will be active.
I cannot certify what the number [of players coming in will be] but we will be active until the end, that is for sure.
Vague allusions to signings may no longer cut it, however, now that Arsenal face the possibility of up to a month without their sole proven holding midfielder.
This is now an emergency situation, and Arsenal need to start acting like it.
One way they can do this is by snapping up one of the promising young holders coming out of France: either Geoffrey Kondogbia or Josuha Guilavogui.
Both were given senior callups for France in the recent friendly against Belgium, where Guilavogui in particular rose to the occasion and contributed to his team's clean sheet while going up against the likes of Marouane Fellaini and Alex Witsel in midfield.
Another is by offering to pay Luiz Gustavo whatever he requires. It would be rather ridiculous if a midtable German club can offer a more enticing contract than Arsenal—Wenger is on record as being able to afford just about anyone at this point.
Wenger could also put in a too-good-to-refuse bid for Fellaini, which would surely make him cringe but would put this fire out rather quickly.
Whatever happens, it is clear that the situation at Arsenal is now an emergency—a lack of urgency in this case is a lack of survival instinct.