In many respects, Arsenal's defensive record this campaign compared to last isn't really that bad. The performances from centre-backs Laurent Koscielny, Thomas Vermaelen and particularly second-year Gunner Per Mertesacker have seen much improvement from Arsenal's 2011/12 campaign. By conceding only 13 goals throughout the season so far, Wenger's men have had their goal successfully raided less than only two teams—Manchester City (10) and Stoke (11), with Chelsea also conceding 13.
The performance at right-back has seen something of a revelation as well—with Carl Jenkinson's stout defensive performances earning his first England cap, deputising for the treatment-table-bound Bacary Sagna. With an alleged £32,000 a week contract recently signed with the club, Jenkinson's performances strike some real calm and confidence into Arsenal fans for the long-term security of the defence of Arsenal's right side.
The issue, however, lies across the pitch.
While Kieran Gibbs, long touted as Arsenal's long-term answer at left-back after Gael Clichy's departure, has been a solid quarter of Arsenal's back four this term, his injury-proneness has been called into question on occasion. Whether Wenger can bank on a talented, but feared-to-be unreliable young defender for years to come, is an increasingly problematic quandary.
Even if Gibbs has proven his adeptness in both his defensive duties in addition to supplanting his wingman, his fitness leaves doubts. Which leaves Andre Santos.
I first discovered Andre Santos while playing Football Manager 2011; as manager of a Guillermo Franco-led Hull City side, I read that, as in reality, Santos had signed for Wenger's Gunners from Fenerbahce—a year in advance, perhaps, but he had still made the trip from Istanbul to play in north London.
So to hear that Santos had signed for Arsenal in "the real world," I felt reasonably confident in Wenger signing an unknown-to-many Brazilian left back approaching 30. And in many ways, some of his performances in his debut season at Arsenal—much blighted by an ankle injury picked up against Olympiakos in Champions League action—had inspired that same confidence in other Arsenal fans.
But even in this still-young season, he has become a much-maligned figure, one of controversy and derision. From his year's ban from driving (for driving at more than double the 70mph speed limit, I might add) to being made Antonio Valencia's whipping boy at Arsenal's visit to Old Trafford earlier in the month, Santos has had, all things considered, a woeful 2012/13 season thus far.
His performances in an Arsenal shirt while deputising for Gibbs have been poor enough for Wenger to see fit to play Vermaelen out of position on the left—something the club captain does, but it is not his preference.
Understanding the reasons for Santos' failures is difficult, for there truly is a myriad of factors. Is he still struggling to acclimatise to the physical, fast-paced Premier League style of football? Has Steve Bould's defensive coaching magic failed to rub off on the Brazilian? Or is he just a poor man's Glen Johnson, bombing up and down the left flank with, at times, seemingly reckless abandon?
The answer is probably part of an amalgamation of all of those factors and more. What is becoming progressively obvious to many Arsenal fans, and surely Wenger, is that Santos might just be past his prime and unfit to a play for a club of Arsenal's standard.
But what does Wenger do?
What can he do, if anything? The Frenchman will understandably want to stand by Gibbs and rightly so. The England international has shown real potential as his country's natural successor to Ashley Cole and Leighton Baines, with his physical and technically adroit showings for his club. But if injury continues to plague his promising career, Wenger will have to step in.
Left-back is Arsenal's weak spot. It needs to be addressed, and quickly.