Roma host the defending European champions on the back of some strong performances this season including a 2-1 win over Italian champions Juventus two weeks ago.
Garcia fully expects the Spanish league giants, who swept Juventus aside 3-1 in last May's Berlin final and beat Roma 3-0 in a pre-season friendly, to be a tough nut to crack at their Stadio Olimpico.
But he said Roma would take a collective approach to countering the threat of Messi, Luis Suarez or Andres Iniesta.
“We don't have an anti-Messi plan, just as there isn't one to stop Suarez or Iniesta,” Garcia told media in the Italian capital on Tuesday.
“As (midfielder) Daniele De Rossi has said, you deal with the threat collectively, both in attack and defence.”
Roma's fans are still hurting from a 7-1 thrashing by Bayern Munich in last season's group stages, a reverse that contributed to the Giallorossi failing to make the last 16.
Barcelona are favoured by many to claim a second successive title and Garcia underlined exactly where Luis Enrique's men are strongest.
“They like to keep the ball and they have lots of pace up top to strike at the right time, making the most of quick breaks,” he said.
“We have to come out well when we have the chance to. Our aim is to get a result based on the quality of our players, thanks to a good team approach in both phases of the game.”
“Although at times we will have to, we won't just sit back and let Barcelona play football. We need to counteract their pressing, a tactic they use when they lose possession and want to win it back quickly.”
“If we do that, we can start thinking positively.”
Roma invested substantially during the summer transfer period with strikers Edin Dzeko (loan) and Juan Iturbe arriving from Manchester City and Genoa respectively and winger Mohamed Salah coming on loan from Chelsea via Fiorentina.
In defence, the Giallorossi have been bolstered notably by the signing of Antonio Rudiger and Lucas Digne, who have both made a positive impression so far this season.
Garcia is still missing creative midfielder Miralem Pjanic through injury, but brushed off the Bosnian's absence.
“There's no point crying about players who can't play, we have to focus on the players we have available and get the best out of them,” he said.
He added: “We all know Barcelona are the reigning European champions. If they're not the best in the world, they're certainly up there.
“We'll play with humility tomorrow but also ambition. We want to qualify for the next round so we need to perform well in all six games.”