If Thiery is not fit he should not start tonight. Not only will it knock him out for a long time afterwards it will more importantly render him unable to contribute significantly during the game. And as I have reiterated before an unfit Henry hampers the rest of the team in that his control and speed are impeded and as most of Arsenal's attacks inevitably go through him, slows the team up. And Arsenal will need to play at a high tempo to catch the opponents off their positions.
He will be much more effective coming off the bench at the later stages if Arsenal have not been successful in breaking PSV down.
How will the match develop?
PSV are most likely to sit on their one nil lead and suck Arsenal in, packing their defence and restricting space behind their lines relying on the counter attack. Arsenal will have to be at their best to break them down. That is play a quick incisive passing game taking as many shots as they can but only when the probability of scoring is reasonable. They should not try to walk the ball in the net!
What they also have to do is vary their game by playing long balls or high balls into Adebayor so that an element of surprise is introduced into their game. There is nothing better for a defender when the opponent's play is repetitive and without variety.
Arsenal need to do two other things:
The first is not to lose concentration in defence as Kone and Farfan can be lethal.
The second is that if they get two nil up they should not sit back but push hard for a third to kill the game off since it is proven that they concede stupid goals.
The probale line up should be:
Djourou Toure Gallas Clichy
Ljungberg Silva Fabregas Hleb
The absence of Eboue is in my opinion a blow since his thrusting runs from defence could have created significant problems for PSV. Really the debate as to whether Henry should play or not should have been replaced by a similar one with Eboue.