As Kolo Toure defended himself against accusations that his lack of height is contributing to Arsenal's vulnerability from set pieces, manager Arsene Wenger was no doubt hoping all 11 players he sends out stand tall against Porto tonight.

The Gunners have conceded four goals in the Premier League and three have come from dead ball situations — the climax of Hull's victory on Saturday came courtesy of an Alan Dawson corner and William Gallas' failure to prevent the tall Daniel Cousin's glancing header.

Wenger admitted his side were vulnerable to set piece delivery after that result but Toure rejected the idea that the lack of a dominating centre-half in the Nemanja Vidic/John Terry mould is the problem.

"We conceded a goal from a set piece against Hull but Cousin played really well and it was a fantastic cross," said the Ivory Coast centre back.

"But we need to be better. I don't have to work harder because I'm not as tall as other defenders.

"I may not be the tallest but I'm one of the top defenders. Roberto Ayala is not that tall and Fabio Cannavaro two years ago was the best player in the world and I'm taller than him."

Considerably so. A World Cup winner with Italy, Cannavaro stands at 5ft 9in while Toure measures exactly six feet.

When manager of Chelsea, Jose Mourinho famously denied meeting Ashley Cole, then an Arsenal player, in a London hotel because he deemed the left-back "too short" at 5ft 8in to sign him.

But the modern game demands full-backs to be both mobile defensively and to add to an attack. Gael Clichy has been excellent in filling Cole's shoes, while Bacary Sagna's 5ft 11in frame gives Arsenal similar options on the other flank.

So it fair to assume that tall full backs, just like tall wingers, are not especially desirable but the great centre-back partnerships have all featured a hulking player who attacks the ball with an almost Neanderthal abandon, partnered with someone adept at picking up the pieces.

Vidic is the rock at the back for Manchester United, Rio Ferdinand the silky ballplayer and pacier of the two.

Terry is the lion-hearted leader of Chelsea, willing to put his neck in where it hurts, while Ricardo Carvalho is regarded as the more intelligent defender whose guile and positional sense snuffs out potential dangers.

Down the years — think Gary Pallister and Steve Bruce, Alan Hansen and Mark Lawrenson and Tony Adams and Steve Bould — one player drops off behind to clean up while the other attacks the ball.

Perhaps the problem lies in the similarity between Toure and Gallas.

Both are capable with the ball at their feet and while Gallas is no shrinking violet, he stands at just 5ft 11in, leaving him, like Toure, vulnerable to players who attack the ball from set-pieces where he is only able to get a standing jump.

"If we have one area where we have experience it is at the back because Clichy, Kolo, Gallas and Sagna, you cannot say they do not have experience," said Wenger, who has options should he wish to change things with Mikael Silvestre fit to make his debut and the promising Johan Djourou in reserve.

"We were less guilty with the corner against Hull, it was a well taken chance. Cousin is very tall, very good in the air and it was a perfect header — it can happen to everybody."

That may be true but when you think of Arsenal's recent struggles against Bolton, it is as much their expertise from dead ball situations as the physical battle that has unsettled the Gunners.

But, then again, Arsenal recently slayed their bogey team with a stunning display in a 3-1 win (Bolton's goal came from a set piece) so perhaps the dead ball dilemma is nothing more than an irritation.

Wenger would certainly have everyone believing as much. "We had a disappointing result against Hull, but I have been sitting long enough on the bench to know that you play this game 100 times and lose it once," he said.

"I believe we will win tonight. We want to make sure we win and get the right belief into the game. This is a different competition. We had a draw at Kiev and know that the home games will be decisive in our qualification."

All three goals in Porto's opening 3-1 win over Fenerbahce in Group G came from open play and the Portuguese champions' expansive style reduces the reliance on set pieces a technically inferior team like Hull focus on.

But chances tend to come with less regularity in Europe's premier competition, making dead ball situations more important, as is the need to be more clinical in front of goal.

There were signs against Hull of the frustrating Arsenal of old that preferred an extra pass when a shot looked obvious — Emmanuel Eboue took this to an extreme on Saturday with an inexplicable square ball when in on goal.

Wenger said: "Porto had a convincing victory against Fenerbahce. Knowing Fenerbahce's team they had a lot of Brazilians and Spanish and that tells you a lot about their quality. We need to take it very seriously."

Arguably the biggest test tonight is for Arsenal to prove against one of the better sides in Europe that their spirit and ability to express themselves has not been irreparably shaken.

Restore their pride with a resounding victory and they really would be walking tall.