Between the combination of injuries and strong partnership between Per Mertesacker and Laurent Koscielny, Vermaelen has found playing time hard to come by. He's appeared in six matches across the Champions League and Premier League this season.
As a result, rumours regarding his departure are beginning to fly. Fellow Belgian Dries Mertens is even actively trying to pull Vermaelen to Napoli, per Belgian magazine Knack (via Goal.com's Matthew Rogerson):
I have already told Vermaelen to come to Napoli 10 times. The city is magnificent and even Benitez asked me to convince Vermaelen to come here. But Arsenal is a great club and it won't be so easy for him to leave.
You can't blame Mertens for trying.
Back in November, Vermaelen quashed any speculation about his future at the Emirates (via the London Evening Standard's James Olley):
Yes. At the moment there is no story. I’m not talking about it. It’s now November but any moment things can happen. If they do, I’m ready and I’m not thinking about anything else.
I can keep talking about my situation. I’ve done that with the national team and I keep on reading stories that I want to leave. But that’s not the case. I’m still focused on the team at the moment and that’s what I want to do. I’m always positive. What I have said is that it is not about my situation but what the team do and I’m really happy that we’re top of the League. Personally I’m still confident I can play for this club and every chance I get I will do a job for this club.
Of course, it wouldn't be the first time a player left shortly after pledging his allegiance to his current club. With it being a World Cup year, Vermaelen may want to move in January if it means more playing time. In addition, Arsenal may feel that his diminished role means the club could do without him.
Look at the Gunners' record when Vermaelen is in the team (via Sky Sports' Matthew Stanger).
And nobody, Goal.com's Christian Nyari included, can pinpoint exactly why the 28-year-old has suffered such a precipitous drop in form.
Now if Arsenal are offered some ridiculous fee for Vermaelen—perhaps in the £20-25 million range—they'd be foolish not to sell him. In lieu of that happening, the Gunners would be much better off holding onto the Belgian defender at least through January.
Arsenal can't afford to be selling centre-backs. If anything, they should be buying them in January. Overall quality isn't a major concern, but depth certainly is.
As things stand now, the club has three natural centre-backs in the senior squad—Vermaelen, Koscielny and Mertesacker. Bacary Sagna has played at centre-back for parts of this season, but he remains a right-back first and foremost and is best out wide.
For a team making a title push and competing in the Champions League, two centre-backs would be nowhere near enough. It would be far from a guarantee that in the event the club sells Vermaelen, it could secure a solid replacement before the window closed.
That means that should Mertesacker or Koscielny go down, Arsenal would be in major trouble. Sagna would be forced back to the centre, and Carl Jenkinson would be playing right-back, which is far from assuring to Gooners.
Things are bad now for Vermaelen, but don't forget the player that he was a year or two ago. He didn't earn the captain's armband by accident.
When Nemanja Vidic was dealing with injuries, he went through some poor runs of form at Manchester United, yet he's remained a solid defender.
Vermaelen's 28 years old, which means he's got another three or four years of solid football left before he really starts declining. Unless he becomes toxic in the dressing room, he will have a role to play at the club, even if it's step down from what he was used to.
Vermaelen is by no means an optimal option for Arsenal at centre-back, but he's at least somebody to alleviate the pressure on Koscielny and Mertesacker. To sell him now would be foolish.