On a day when Arsenal's UEFA Champions League victory over Olympiacos is being dissected, thoughts should instead be turning to Saturday's trip to West Ham. The game will be a defining moment for Arsenal's season, one way or the the other.

While last night's uneven performance raised as many questions as it offered answers, it's still the Champions League group stage. A win is all that matters at this point, regardless of style. Qualifying from the group and progressing to the real tournament is the only objective.

It is instead in the English Premier League, where the quality, strength and character of this new-look Arsenal squad will be revealed. Away fixtures like the one on Saturday provide the most graphic examination of all of those attributes.

Dealing with the obvious first, this is another chance for Arsene Wenger to renew hostilities with his antithesis, Sam Allardyce—the man whose footballing philosophy usually brings to mind words like "rough" and "direct," yet can still be seen communicating through an electronic earpiece and sometimes using a laptop in the dugout.

Yet for all of his stylistic and cultural contradictions, Allardyce has used his craven and brutal formula to frustrate Wenger on numerous occasions. That's why, like him or not, Allardyce represents a physical and psychological barrier Arsenal must cross before anyone takes them seriously.

For instance, Arsenal's foibles from set pieces are sure to either improve or get worse following an encounter with Allardyce's team. Make no mistake, in between trying to kick Arsenal off the pitch, or to use the accepted modern football parlance, "playing a physical game," West Ham will challenge the Gunners with an aerial bombardment at every opportunity.

It's a formula Allardyce has distilled into a malevolent science and, again, like it or not, it is certainly effective. More than one goalkeeper has found himself bundled over the line by a burly centre forward whose main job is to prevent a clear run at the cross.

So an acid test surely lies in store for Vito Mannone, just as it does for the middle of Arsenal's back four. West Ham may have their biggest aerial threat back for Saturday's game.

Andy Carroll came on as a substitute in the Hammers' 2-1 away win over Queen's Park Rangers. It seems the fates may have conspired to conveniently bring Carroll back against the one team he could dominate, and he's certainly troubled Arsenal in the past.

That's why there can be no room for Laurent Koscielny on Saturday. His clumsy and ill-suited partnership with Thomas Vermaelen cost Arsenal against Chelsea and threatened to do the same against Olympiacos.

Per Mertesacker apparently missed last night's game due to illness, after being replaced for the visit of Chelsea, because of the style of the opposition. Well then, if Wenger is true to his word regarding stylistic concerns, then Mertesacker has to make his return against the Hammers.

Other than with the aid of one or two phone books to stand on, there is no way Koscielny can compete with the styles of Carlton Cole and Carroll. Winger Matt Jarvis ensures West Ham can rely on accurate and testing delivery into the box, so Mertesacker's height is essential.

However, that's only after Arsenal win the fight, or at least match it, in open play. Diminutive playmaker Santi Cazorla will have to be tenacious enough to avoid being crowded out by a rugged West Ham midfield.

The group contains longtime Arsenal tormentor Kevin Nolan and the underrated Mark Noble. Certainly the Gunners will need to rely on Mikel Arteta's smarts and intensity to help hold things together.

Arteta epitomises the kind of resilience Arsenal have shown more than once this season and will certainly need against the Hammers. Strong characters like Lukas Podolski and Vermaelen must also help carry the fight to West Ham and ensure Arsenal won't be intimidated by Allardyce's tactics.

During Wenger's tenure, Arsenal have often been victimised by the harsh realities of a footballing culture that accepts brutal cynicism as "just part of the game." However distasteful these realities may be to those who admire the creative aesthetics of Arsenal's play, they are still hurdles the team must clear if they hope to end their trophy drought.

That's why Saturday's trip to West Ham is a crucial barometer of what, if any, progress Arsenal have made this season. It's more important even than the Chelsea clash, which could be explained, however thinly, by the eternal optimist, as a battling defeat against a top title contender.

However, a defeat to a team that roughs Arsenal up and dominates in the air, while stifling open football with a rigid defensive wall, will confirm everyone's worst opinions about Wenger's team. Sadly they'd be right, because when the final whistle sounds at Boleyn Ground, if Arsenal have been bullied and succumbed to two set-piece goals, it will mean that only the faces have changed.

The same old problems will remain, and that will mean another season stuck in neutral for the Gunners.