Considering the way Cole has been playing for most of the season I wouldn't be surprised if that ankle injury had been sustained over the summer. And that's only half-joking*. However poorly Cole's been playing, however, this isn't good news - dropping Ryan Bertrand straight into the fire because you're forced to isn't really the best way to introduce him to Premier League football.
*A Cole injury during the summer would explain both his terrible play and the out-of-nowhere Alvaro Pereira chase.
Also, remember when we had some Russian dude who could fill in at left back and left midfield? Good times.