Koscielny is clearly a talented player who brings a diverse skill set to the table. In general, his positional play is strong, though he has a few questionable tendencies that could get him in trouble in the fast-paced, physical Premier League.
Could he be a starting center-back for Arsenal come August? Probably yes, though he would surely experience some growing pains against first-class opposition.
Should Koscielny and Vermaelen be partnered as the Gunners' starting central defensive pairing? Probably not.
They're too similar in their strengths and their weaknesses, for one.
Vermaelen's incredible offensive contribution often made up for his persistent tactical errors in 2009-10. Like Koscielny, last season Vermaelen had a tendency to drift forward, to over-aggressively bite on plays up the field instead of holding a solid back line.
With the experienced William Gallas or Sol Campbell to cover for him, Vermaelen was rarely exposed. With both out-of-contract veterans likely to sign elsewhere, Vermaelen would be called on to play mentor to a player a month older than himself whose positional play is equally shaky.
Another important consideration is preferred position.
Before joining Arsenal from Ajax, Vermaelen played left center-back, a position that was available for him upon moving to Ashburton Grove. Koscielny is a left center-back at Lorient.
Who would move to the right side, and would either be well-suited to the new role?
I believe Koscielny will be a strong signing for Arsenal and well-worth the £8-10 million that some believe it will take to convince Lorient to part with him. However, it seems clear that he is not ready for the full-time starting job and that his style of play and physical attributes are too similar to Vermaelen's for them to be effectively paired at this point in time.
As it is, right-footed, 6'3", 23-year-old Johan Djourou might actually be the best man for the job, though he has to be regarded as a complete wild card at this point.
His injury-plagued last three seasons have relegated him to the fringe of first-team relevance, but when healthy, he has proven an excellent young player.
Unlike Vermaelen and Koscielny, Djourou has been in the system since his youth career and has spent time with the first team over the last five seasons. He is relatively inexperienced, to be sure, but he has a tremendous upside, and with a solid backup behind him, he may be ready to take the reins this season.
Ideally, of course, Arsenal would benefit by signing an experienced right center-back from outside the organization. At a position in which so much depends upon experience and judgment, it would be irresponsible to trust a new player who has never played right center back, or a young player who has been injured more often than not over the last three years. Youth is relative; experience is everything.
I have faith in Arsenal's player development model, but there is simply nobody in the system who is ready to step into the role. Koscielny seems too wet behind the ears to step up to the Premier League and into a new position in an unfamiliar formation.
This may be the year in which Arsenal's increasingly battle-hardened youth contingent announces its arrival across Britain and Europe. An inexperienced, gaffe-prone central defense, however, could easily sap Arsenal's title aspirations before they even get off the ground.
Vermaelen, Koscielny, and Djourou are all excellent players, but is this the season to have three comparatively inexperienced center-backs and one youth call-up as the team's only options at a critical position?
In Wenger I trust, but in experience I believe.