The Arsenal skipper is expected to return to the squad for tonight's crucial Champions League clash despite having not trained fully for the past two weeks.

Henry has been struggling to shrug off a troublesome hamstring injury as well as a foot problem - and was given a painkilling injection to play in the first leg a fortnight ago.

Gunners boss Arsene Wenger knows the season could effectively be over for Henry should his gamble on the striker's fitness go horribly wrong tonight.

Former Barcelona defender Koeman, however, can understand why it would be considered a risk worth taking.

"Psychologically for Arsenal it is very important that Henry is there," said the PSV coach.

"Henry is basically the face of the team and the other players play better in his presence.

"I have read this is the most important game of the season because there is not much more to win for Arsenal.

"Under those circumstances you are more willing to take some risks with a couple of players.

"A fit Henry is very difficult to defend, so that could be a problem."

PSV hold a slender 1-0 advantage from the first leg, after which the Dutch side were criticised by Wenger for a perceived negative approach.

Koeman reflected: "It is possible we could play the same way as the first leg, but we could also chose a different strategy.

"It is also possible to play a bit more than compared to the home game to score goals.

"Even with our own problems, we are still capable of giving them a surprise. It is in the character of our players.

"It is about defending well, about having good organisation.

"That is the basis of Dutch teams, because in terms of quality, our players may be a bit less but those are points where you can actually win."

Koeman added: "We are not going to open up and let Arsenal have it all their own way, because then you are not going to win.

"I expect Arsenal to try to score.

"They have played that way for years and have been very successful."

However, Koeman warned: "If we score tomorrow, then it will be very difficult for them.

"But Arsenal are a team which plays fast football and that is how they create their chances - so they could score three because they have that quality.

"However, when you lose 1-0 (in the first leg), then you always have the thought in your mind that you can also get a goal against you - then you would have to score three.

"You can play a great game, but with a few seconds left you can let in goal and then you say good bye to the Champions League."

Koeman has a few selection worries ahead of tonight's match.

Striker Patrick Kluivert has a back problem, while defenders Michael Reiziger (stomach) and Manuel da Costa (virus) are also out, along with former Liverpool right-back Jan Kromkamp who has a hamstring injury.

Ibrahim Afellay, meanwhile, has complained of a similar problem and could miss out.

Midfielder Timmy Simons maintains the depleted PSV squad will pull together to get a result.

The Belgian said: "We are all willing to work hard for each other, there is a great spirit within this PSV team.

"We are in a good position now, but Arsenal proved that they are capable of great things at home so it will be difficult.

"They will be cautious as well because one goal against them will be deadly, so they will be looking for the right balance between defence and attack."