The Gunners could be without influential captain Cesc Fabregas, who is struggling to overcome a leg problem.
Barcelona, meanwhile, may be missing Andres Iniesta, but still have plenty of players who would leave most defenders with sleepless nights.
Limbering up: Vermaelen trains on Tuesday before facing Messi
However, Belgium international Vermaelen - who returns after missing the 1-1 Barclays Premier League draw at Birmingham - insists Arsenal must not get hung up on reputations.
'We are not focussed on individuals, because we have to play our own game and play as a team,' Vermaelen declared.
'You are aware of the qualities of the opponents, but you also know what your own strengths are.
'Messi is a very good player, one of the best players in the world. Of course you enjoy watching him play, because he is a real footballer.
'However, there will be no time to be intimidated tomorrow. You do not have to be nervous or look at individual players. You have to be focused on your own performance and the team's performance.
'You cannot look at how great Messi is, because you have to play your own game.'
Vermaelen is confident Arsenal can rise to the challenge.
'It is one of the biggest games you can play in, against one of the best sides in the world,' he said. 'However, it is important to play as a team and hopefully we can show how good we are.
World beater: Messi (right) shines brightest in Barca's team of stars
'We have to be mentally strong and we have shown that this season. If you want to win the Champions League, you have to beat the best teams.'
The Belgian has been one of the most consistent performers this season since his summer arrival from Ajax.
However, Vermaelen maintained: 'I have no time to be proud. I am still only 24 and there is room for me to develop as a player.
'I am happy at the moment, but things can be better in the future.'
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