Far and away (and fairly, in most cases), the defensive performances Arsenal have delivered this season have attracted more scrutiny and scorn than in recent years. A big reason has been the injuries suffered to Laurent Koscielny and summer signing Mathieu Debuchy.
By themselves their absences would be hard to overcome, but they're coupled with a defensive roster that's already short in numbers to begin with. Leads that Arsenal should have comfortably tucked away as victories have instead resulted in draws or losses, each of them for numerous, specific reasons that may not be explained away as something the two could have prevented on their own. It's hard, though, to not think the leads would have been converted to wins if they were healthy and playing regularly.
Today, during his routine pre-match press conference, Arsene Wenger confirmed one of the two long-term defensive absentees is back training and, more importantly, fit enough to be named to the squad for tomorrow's crucial Champions League match versus group leaders Borussia Dortmund:
He’s (Koscielny) in the squad for tomorrow. It’s very good news because he was out for a while now and we are short in numbers defensively. It’s good to have his quality back.
Similar to Olivier Giroud, Koscielny appears to be back quicker than initially expected, with Wenger going on record in early November saying the defender would miss an additional month or so.
Wenger's known for not rushing players back into the starting lineup after a lengthy spell away, so there's still a likely chance that Koscielny's replacement, Nacho Monreal, will get the nod. Monreal quietly put in a wonderful performance versus Manchester United this past weekend, and he seems to be growing in confidence as he adjusts to his makeshift role.
The boss also said today that Jack Wilshere (ankle), Theo Walcott (groin), and Wojciech Szczesny will be out of the squad, with Danny Welbeck (hamstring) making the squad but with an unknown starting lineup status.