Garcia's men travel to San Siro hoping to secure a victory that would cut the gap to Serie A leaders Juventus to three points after the champions secured a 4-0 win over Sassuolo on Sunday.
Milan, in contrast, are 25 points off the pace in 12th, and edged into the last 16 of the UEFA Champions League by virtue of a 0-0 home draw with Ajax last week after playing much of the game with 10 men following Riccardo Montolivo dismissal.
But former Lille boss Garcia is adamant that Roma face a difficult task if the three-time champions are to take all three points, earmarking Mario Balotelli and Kaka as the hosts' main threats.
"Everyone knows Milan have players of a high level and you can't qualify from the Champions League group phase without a strong side," he said.
"We know that playing away to Milan is more difficult, but we will take our usual approach. We are going to Milan in order to win. It will be tough, but that is our ambition.
"They are great players, we all know that. Balotelli can score at any moment, while Kaka is a complete player and one I like very much. We must do everything to close down space around these players, but Milan isn't just two men."
Roma have put themselves in contention for the title with their unbeaten start in Serie A, but Garcia is not getting ahead of himself.
"We're a long way from the end of the season and won't think about what Juventus or any of the others are doing, so we focus only on our own results," he added.
"We are ready after a great performance against Fiorentina and a good result at San Siro would be a further step forward.
"The Scudetto? We'll see at the end. I will just say we'll need a final sprint with the favourite teams, who are in my view Juventus and Napoli, but why put extra pressure on the team?"
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