One voice is telling me that 1-0 was a good result . . . especially given Arsenal's proven ability to score on the road in Europe . . . and that the glass is very much half-full. However, another voice reminds me that the one or two missed chances at Highbury could be costly in the end.

There's this nagging feeling which will probably be shared by most of the club's supporters, that Villarreal were let off the hook. It's a case of what might have been. Think in particular of Philippe Senderos's header that floated harmlessly over the bar, and the second-half chance that Thierry Henry would normally have taken on and finished. Arsenal were not as composed in front of goal as might have been expected.

That's what you get when the stakes are high and when a group of largely inexperienced players is closing in on a major final.

For the first time in a while, Cesc Fabregas's passing was not up to its usual standard. Because he was operating in such a congested area, he wasn't as influential as we've become used to, and he was never able to release Henry with the perfect ball. Against that, he's likely to find it easier in the second leg when Villarreal will have to force the pace.

Emmanuel Eboue also struggled during the first half, and his indecision clearly unsettled Kolo Toure, but to Eboue's credit, he was much more effective in tandem with Alexander Hleb down the right later in the game and, like Fabregas, he will probably be more comfortable with Arsenal's second-leg approach of soaking up pressure and attacking on the break.

In a sense, Eboue's performance mirrored Arsenal's performance. Not perfect by any means, but determined and committed enough to create an advantage that should be enough to take them through to their first Champions League final.

There was the added frustration of what appeared to be a legitimate goal by Henry ruled out by the linesman. I was right in line with Robert Pires as he played the ball, and my initial impression was that Henry was offside. It was only when I saw the replay that I realised that Henry was fine, and that Freddie Ljungberg was in fact in an offside position.

Henry was travelling at pace, and Ljungberg was in close attendance, so it was a hard call. Was Ljungberg inactive?

Well, you would have to say that he would have gone for the ball if Henry hadn't, and it comes down to a question of interpretation. Arsene Wenger mentioned afterwards that in the absence of a video replay, it would be wrong to criticise a linesman over such a tight call.

A few of the subsequent offside decisions that went against Arsenal were much more dubious, but matters probably evened themselves out after Villarreal thought they might have had a penalty when it looked as if Gilberto brought down Jose Mari just inside the box. Again it wasn't clear-cut, and the fact that Arsenal were the home side could have swayed the decision.

AC Milan don't find themselves in nearly as strong a position as Arsenal, but they also will have been frustrated by the opportunities they missed. For all the sublime quality of some of their passing, and despite Ronaldinho's moment of inspiration in creating the goal for Ludovic Giuly, Barcelona are not racing certainties to go through.

Admittedly, while Arsenal's chances of reaching the final are about 70 per cent, Barcelona's have to be 80 per cent, but if they had won 1-0 away from home against one of the lesser sides in Europe, then you would expect them to finish the job emphatically at Camp Nou. Even though Milan are on the back foot now, I just don't see that happening.

If Carlo Ancelotti can get his players in the right frame of mind, and if he brings Paolo Maldini in and pushes Serginho forward, and if he replaces Clarence Seedorf . . . whose contribution was negligible in my book . . . possibly with Massimo Ambrosini, it could still be a fascinating contest.

Milan clearly have the experience, it's just that at the moment, their self-belief is in doubt. They will have to hope that Ronaldinho and Barcelona feel the weight of expectation, but as Ronaldinho showed at the San Siro, he has the necessary vision to deliver the perfect pass from anywhere on the pitch. He remains the x-factor that no defence can legislate for.

While Arsenal won't underestimate the ability of Juan Roman Riquelme, he is not in the same class as Ronaldinho.

Gilberto wasn't given a man-marking job in the traditional sense at Highbury as he left Riquelme and made forward runs when Arsenal had possession, but once the ball broke, he and Fabregas moved in to close the Argentinian down. Wenger doesn't over-analyse the opposition, but it was clear that he had a plan in mind for Riquelme.

It's a fair bet that you won't see Gilberto as involved in the game when Arsenal have the ball on Tuesday. Obviously, if Villarreal get a goal, everything changes, but for as long as it stays 0-0, Wenger will employ very similar tactics to those that proved so effective in Madrid and Turin.

Arsenal will wait for the opening to come through Henry, and they'll also pressurise the Villarreal defence at set-pieces. The Spaniards will have been encouraged by how the first leg went at Highbury even though there was no doubt who was the superior side. Notwithstanding the gamesmanship, they battled well following Toure's goal and I thought that Cesar Arzo held the defence together impressively, and that Riquelme came more into the game during the second half.

If Barcelona have already reserved their hotel in Paris for 17 May, Arsenal have made a provisional booking. Both teams should make it through, but neither will have it easy.