It's not often that Arsenal spend £12m on a player and not have him be an automatic first choice player. They have, though, on Olivier Giroud, and, if all goes as expected, he will compliment, not supplant, Robin van Persie. Even if van Persie leaves, the likely in-house replacement for him would be Lukas Podolski; among Arsenal's strikers, Podolski best replicates the movement of van Persie; like van Persie, Podolski can drop deep and rotate with wide players and create from deep. Giroud's movement is different; he doesn't drop deep as much, and is more of a traditional target man who can hold up play and link up with his wide players.
Like van Persie and Podolski, though, his movement in the box is exceptional, and, unlike Marouane Chamakh, he isn't afraid of shooting, doing so 4.5 times per game for Montpellier last season (van Persie shot 4.6 times per game, Podolski 2.9 per game for a team that didn't have much possession, and Chamakh a measly 1.8 shots per game in 2010/11). As Chamakh's scoring drought got worse, he went back into his comfort zone, which usually meant dropping deeper and deeper, and farther away from goal. He seemed to play best last season when he was partnered with Robin van Persie, and although Giroud is on the record with his preference for 4-4-2, he showed last season that he's very adept as playing as the lone striker.
The fact that Giroud doesn't drop deep as much as van Persie, though, doesn't prevent him from being a starting player for Arsenal or being a key player for Arsenal. It does mean, though, that he'll probably start his Arsenal career off the bench, getting acclimated to English football and to Arsenal, but also, letting Arsenal get acclimated to him.
What he does give Arsenal straight away, though, is a different option, either to start or to come off the bench. Giroud has been likened to a young Didier Drogba, and the comparison doesn't seem too off; like Drogba, he excels at winning the ball in the air, winning 70% of aerial duels last season. The manager agrees, saying
He has a very good physical presence and is exceptional in the air, with a great work ethic. We are excited about Olivier joining us and he will add an additional dimension to our attacking options next season.
Like Drogba, Giroud is also very powerful with the ball, and is a valuable asset in the penalty box. Furthermore, his ability to link up with players, while not as good as van Persie's or Podolski's, is still good enough that Giroud was able to contribute eleven assists, many of which were cutbacks, crosses and even a through-ball, to go along with flick ons from headers.
The big question for Arsene Wenger, then, is how to integrate Giroud into the starting lineup. Bringing him on as a sub won't be so much of a problem, as he'll either come on for Robin van Persie or join him in Wenger's desperation 4-4-2 (or in a game that's already won). A return to the 4-4-2 that was utilised by the Invincibles is possible, but only if Arsenal can get the balance right. The concern for Wenger would be the makeup of the midfield; would there be enough creativity and technical quality to justify the loss of an extra midfielder, and, would Arsenal suffer from the loss of a midfielder when they routinely face three man midfields?
Given the tendency of opposition midfielders to play deeper, the loss of a midfielder in the attacking phase may not be such a problem, especially given the excellent controlling ability of Mikel Arteta. In the defensive phase, one of the strikers, probably van Persie, would have to drop deeper to give structure to Arsenal's pressing game. There would, though, have to be extra creativity from the wider areas, to make up for the lesser amount of creativity from the middle.
Van Persie could, though, play behind Giroud in a role similar to Wayne Rooney's role at Manchester United, where he instigates attatcks and then finishes them in the box, and also similar to the one that Shinji Kagawa played at Borussia Dortmund. There, control of the midfield was executed through the deeper-lying playmaker tendencies of Sven Bender and Nuri Sahin (later Ilkay Gundogan), with both providing creativity, that also came from the flanks in Mario Götze. If Arsenal can replicate that with Alex Song and Mikel Areta, using van Persie in that role could be possible; if he were to be marked out of the game by a defensive midfielder, he could always push forward.
He undoubtedly has the technical quality to play in that role, and probably play well, but it might not get the best out of his ability. For that reason, a 4-2-3-1 with van Persie as the number 10 probably won't be utilised, but, a 4-4-2 could be, especially against teams that sit deep against Arsenal. In that sense, Giroud will offer something different, by allowing Arsenal to go more direct and bypass the midfield, something that could help them continue to be dangerous even if they're under pressure, by allowing Robin van Persie to get the ball in threatening areas.
In games where Arsenal were placed under pressure, they lacked an outball; Giroud will give them one, and he will also give a partner for van Persie to counterattack with, along with Theo Walcott. By giving Arsenal other dimensions, Giroud will make them more dangerous. And unlike Marouane Chamakh, Giroud is a true target-man striker, someone who isn't afraid to take shots. At a total price of £22m (transfer fee+wages over 5 year contract), Giroud is likely to be double his money's worth.