The Italian keeper was not happy with Paris Saint-Germain's display against Bordeaux and is demanding more against Manchester United.
Paris Saint-Germain have to improve their attitude if they are to beat Manchester United in the last 16 of the Champions League, Gianluigi Buffon has warned.
The French champions face Ole Gunnar Solskjaer's resurgent side at Old Trafford in the first leg on Tuesday.
Under caretaker manager Solskjaer, United have won 10 and drawn one of their last 11 games in all competitions, with a 3-0 victory at Fulham on Saturday lifting them back into the top four of the Premier League.
PSG are 13 points clear at the top of Ligue 1 thanks to their 1-0 win over Bordeaux, but Buffon was not impressed with their display and insists they must improve against the Red Devils.
100% - Paris (12/12) are the only team from the top 5 European leagues to have won 100% of their home league games this season. Cool. pic.twitter.com/ZRnmLKSytA— OptaJean (@OptaJean) February 9, 2019
"Apart from the win, I didn't like the game," he said after the match. "I think we have to improve in terms of mentality, attitude and the spirit of sacrifice for the team.
"A very important game is waiting for us on Tuesday. We have to play a big match. To play against this team, you need to be stronger, more solid, with a different attitude.
"Are we favourites? No, I think we're level, it's 50-50."
PSG were dealt a blow when Edinson Cavani, who scored the winning penalty against Bordeaux, was unable to come back out for the second half due to injury.
Head coach Thomas Tuchel has admitted both the striker and midfielder Marco Verratti could be forced to miss the United game.