Theo Walcott is out until next season. His injury robs Arsenal of a uniquely speedy, creative and clinical winger who was the club's leading scorer last season and was beginning to have a significant impact after returning from an injury earlier this season.
The silver lining, however, is that Walcott tore his ACL right as the January transfer window opened. Arsenal have had time to scope out a short-term replacement and determine if Walcott's absence necessitates a signing.
If Arsene Wenger decides to go that route, he might have a look at these four players.