Arsenal's central defense: less is more?

Following up on last week's goaltending post, the other main area of concern for most Arsenal supporters during the 2009-10 campaign was the center of defense.

As of right now, assuming that William Gallas will not be at the club for 2010-11, and that Sol Campbell might not be as well, and that Mikaël Silvestre might also be gone, Arsenal have essentially three senior central defenders: Thomas Vermaelen, Johan Djourou, and Kyle Bartley.

Vermaelen is clearly first-team quality, and Djourou has shown promise when he's been healthy.  Kyle Bartley played in the Carling Cup last year as well as in the Champions League match against Olympiacos.  It is clear, though, that Wenger needs to sign at least one central defender, if not two or three.

But does that not raise a question?

Assume, for a moment, that Arsenal were to sign Laurent Koscielny from Lorient.  That gives the club three workable first-team defenders, plus a young up-and-comer in Bartley.  If one buys into the idea that a consistent center-back pairing is desirable (as Arsène Wenger does), and assuming health is no issue, one would think that Vermaelen would pair with Koscielny at the back for most, if not all, Premier League games, with Djourou filling in when necessary.  The Champions League would see one or the other occasionally coming out for Djourou or even Bartley, depeding on how crucial the match was.

But then, of course, there is the FA Cup and Carling Cup.  With basically two matches per week for the first three months, a three defender rotation might not be workable.  However, the question becomes, then, when to stop.  Is five too many?  Is six too many?  Or is six necessary, given the trouble Arsenal were in before the arrival of Sol Campbell in January this year?

Or is six too many, because if health is less of an issue, the club will have two or three defenders sitting on the bench, rusting away, and potentially grumbling?  The balance between having adequate depth and having players who are engaged, happy, and productive is never easy to strike.  Four seems like the minimum amount, but if Djourou cannot find form or if any of them get hurt again, suddenly it's looking thin.  On the other hand, if Wenger has six again, three may never see the light of day beyond the Carling Cup.

If you had your druthers, would you like to see Wenger bring in fewer or more central defenders for 2010-11?