Barcelona are the reigning champions and dominated the previous encounter
between the teams in September but Milan still came away from the Camp Nou
with a 2-2 draw.
And although his team are favourites, Guardiola is taking nothing for granted.
"We need a perfect match to win here. Milan have changed since the first match, they can kill you on the counter-attack, especially when Pato plays," he said.
"Ibra (Zlatan Ibrahimovic) is very good. They're used to having a lot of possession and they're good at set-pieces."
"They have everything and that's why they're aiming to win the league and the Champions League. We can't afford to be at 70-80 percent but I know that we'll be the same as always tomorrow."
"We won't play for a draw, we'll try to win so the fans can watch a great match. It's a test for the future in the Champions League and to show our opponents that we're still us."
Barcelona don't need to win the game as a draw will be enough to keep them top of Group H ahead of their final match at home to minnows BATE Borisov.
Milan, however, know that anything other than a victory will likely result in them finishing the group in second as they travel to Czechs Viktoria Plzen in their final game.
"It's always better to win the group rather than come second so you can play the second leg (in the last 16) at home," said Guardiola.
"Coming here is an honour, playing Milan you can feel the history and tradition, you're aware of the prestige of this club. And we'll try to win so we can have the prestige of doing so against a team such as this."
The major danger for Barca should come from former forward Ibrahimovic, who Guardiola opted to sell after just one year and replace with David Villa.
That decision meant Ibrahimovic was seen by many as a flop and there are rumours that the Spanish boss didn't like the big Swede.
Ibrahimovic himself claimed Guardiola ignored him but the Barca boss says he has no ill feeling towards his former charge.
"If I see Ibra of course I'll say hello to him, he helped us a lot the year he was with us," said Guardiola.
"He's had a fantastic career as a player and that doesn't change because he didn't say nice things about me. I don't have any problems with Ibrahimovic."
Barca captain Carles Puyol says it won't be easy to stop Ibrahimovic.
"Man-to-man marking is difficult you need the whole team to stop him," he said.
"What Ibra wrote in his autobiography doesn't give us extra motivation because you don't need that when you play against Milan. I think Ibra is proud to have played for Barca."
"I've always admired Milan and their way of working and I support them when they're not playing against us. We always play to win and we'll see what happens, a draw could be enough but we'll try to win."