Arsenal v Barcelona: Lionel Messi admits Spaniards are scared of Theo Walcott's pace in Champions League

“I can only speak from experience but he was one of the most dangerous players I have ever played against,” said Messi. “Barcelona players are not scared easily but I can tell you that when we played Arsenal last season he truly worried us.”

Some praise — and an assessment that was vindicated by the evidence of the two Champions League matches last season.

In the first leg at the Emirates, Arsenal had been overrun and were trailing 2-0 until the introduction after 67 minutes of Walcott, whose goal and cameo performance rescued a 2-2 draw.

Walcott was similarly influential at the beginning of the second leg, providing the assist for Nicklas Bendtner's goal at the Nou Camp that briefly put Arsenal ahead before they succumbed to a display of authentic individual genius from Lionel Messi, losing 4-1 and 6-3 on aggregate.

It secured Barcelona’s place in the Champions League semi-finals for a third consecutive season, but the threat of Walcott has remained imprinted on their minds.

Pep Guardiola, the Barcelona manager, described Walcott as quicker than “our whole team put together” and memorably observed that, once he had the ball, you needed a pistol to stop him.

He wryly noted that Barcelona’s answer should simply be to stop Walcott getting the ball.

“When we were playing Arsenal at the Emirates we were so in control of the game at 2-0, with all respect Arsenal were not even in the game,” said Messi.

“Then Theo came on and changed the game. He pretty much single-handedly salvaged a draw that night.”

While Walcott was very much a squad player last season, the improvement in his delivery and finishing has elevated him to a regular place in Arsène Wenger’s starting team.

His 10 goals are already the most he has scored in a single season and he is adamant that, both individually and collectively, Arsenal should offer a much greater threat to Barcelona in Wednesday’s last-16 first-leg tie.

“We are better without any doubt,” said Walcott. “They taught us a lesson but the lesson has been learnt. We have bags of experience now. We have just got to take the way we have been playing in the Premier League into the Champions league.

“I believe that we can do much better than last season; we can’t do any worse to be honest. There is so much confidence in the team. We know what to do.”

There is an acknowledgement at Arsenal that they were just too respectful of Barcelona last season, particularly in the first half of the first leg.

Indeed, it was not until Walcott came on that they really had a player who was willing to get behind their midfield and run at the defence.

And if there is a way to threaten Barcelona, with their great emphasis on possession, it is surely through rapid speed on the counter-attack.

“We needed an extra 10 minutes in that first leg,” Walcott told Arsenal TV. “As a substitute, you want to make a reaction any way you can.

"I think I surprised them with my pace. We didn’t have anyone who went in behind them because they had so much of the ball.

“It was only so long it could last. I surprised Maxwell [for the first goal]. I came in behind him and tucked it away. That inspired us to get the result we wanted.

"I’ll try and do something if I come off the bench but I want to be doing that in the starting line-up.”

With Samir Nasri unlikely to be used as anything more than a substitute – he will have a final test on his hamstring on Tuesday morning – Walcott is almost certain to be granted that wish.

Wenger has suggested that Arsenal must play their usual attacking game against Barcelona but, according to Walcott, there will be two key caveats.

Firstly, they must restrict Messi, and, secondly, their artistry on the ball must be matched by their industry off it.

“Messi was fantastic at their place but overall we have just got to keep him quiet,” said Walcott.

“Defensively, when we lose the ball we try and win it back as quick as we can now. That is what we did against Chelsea and Manchester City — and we have to take it into the Barcelona game.”

Wenger has stressed that Arsenal’s priority should be the Premier League but, with Barcelona arriving in London on Tuesday afternoon, there is no disguising a special excitement among the Arsenal players.

“It’s going to be massive; the biggest one I’ll play in,” said Walcott. “It’s going to be a great, great battle. It will be a very open game. It’s a great game for the neutral to watch — and just to be part of it is a dream.”

Walcott also has the attributes to be Barcelona’s worst nightmare.