The French giants, who go into the first leg of their last-16 Champions League clash on the back of three unconvincing results, will face a United side in fine form.
Ole Gunnar Solskjaer has won 10 of his 11 games in charge since taking charge and Buffon admits PSG must up their game to avoid defeat at Old Trafford.
Speaking after Cavani penalty earned PSG a 1-0 win over Bordeaux on Saturday, Buffon said: ‘I appreciated the victory but I did not like the match.
‘We have to improve mentally and in our attitude, to have more of a spirit of sacrifice for the team.’
Buffon is in no doubt that they must put in a much improved performance to keep their hopes of reaching the quarter-finals alive.
‘On Tuesday we have a very important match and we will have to do better,’ he said.
‘I believe we have to get better in everything because we will play against a team and in a stadium which will oblige us to be more solid and have a different attitude.’
PSG will be without Cavani, who picked up a thigh injury at the weekend, and star man Neymar, who is suffering with a foot problem.