A second-half winner from ex-Napoli striker Gonzalo Higuain sent Juve four points clear of Roma
A second-half winner from ex-Napoli striker Gonzalo Higuain sent Juve four points clear of Roma, with Napoli now seven points off the pace after AC Milan and Lazio won on Sunday to move into third and fourth places respectively.
Although Juve coach Massimiliano Allegri paid tribute to his squad for "interpreting the game well", Buffon said it's not enough.
One of the world's most decorated goalkeepers, former World Cup winner Buffon has yet to win a Champions League title and at 38, time is running out.
Juve host Lyon in the Champions League on Wednesday looking to secure their place in the last 16 -- a win would see the Italians seven points clear of the Ligue 1 side with two games remaining.
But if the Italian giants are to beat the likes of Real Madrid, Bayern Munich and Barcelona to the top prize in European club football, Buffon said a step up in "quality" is required.
"It was a great win for us against a strong side that we all respect. Napoli made us suffer," said Buffon.
"But we have to improve certain aspects of our game, and we're still struggling to put the instructions of the coach into practice on the pitch.
"Morale is high. But, I have to say again: if we want to enjoy a good run this season, especially in Europe, the quality of our game has to improve."
Napoli face Besiktas away on Tuesday looking to relaunch their Champions League campaign after a shock 3-2 defeat to the Turks at the San Paolo two weeks ago left them in danger of losing top spot in the group.
And in Serie A, Maurizio Sarri's men have even bigger problems.
After selling Higuain to Juve for an Italian transfer record fee of 90m euros, Napoli are still without a proper centre-forward after the Argentine's replacement, Arkaduisz Milik, was sidelined with a knee injury.
"We lost one of the best forwards in the world and the club made the decision to buy young players," Sarri lamented after Saturday's defeat.
Roma, runners-up twice in succession in 2014 and 2015, are now seen as Juve's principal rivals, although dropping points against supposedly inferior opposition -- as they did in a scoreless stalemate at Empoli on Sunday -- will prove costly.
Roma striker Edin Dzeko remains top of the league scoring charts on 10 goals, but the Bosnian was among the players who hit a blank at the Castellani stadium, where home 'keeper Lukasz Skorupski performed heroics.
Roma sit second at four points behind Juventus, but midfielder Daniele De Rossi said getting past Empoli's astute defence was not easy.
"It would be a mistake for any side to come here and think they can simply score by shooting once they get into the area," De Rossi told Sky Sport. "Empoli defend very well."
Napoli's defeat gave AC Milan and Lazio an extra incentive and both seized the day to jump up the table to sit third and fourth respectively.
Giacomo Bonaventura's 49th minute free kick broke the deadlock at the San Siro although Milan endured a nervous finish to put the smile back on coach Vincenzo Montella's face following a 3-0 midweek defeat at Genoa.
"That was a great victory, but a very difficult match. We knew it would be like that," Montella told Sky Sport.
"Credit to Pescara, they created a lot of problems for us."
At the Stadio Olimpico, Senad Lulic opened the scoring after Keita Balde's cross came off goalkeeper Andrea Consigli and back off the Bosnian midfielder before landing in the net.
Ciro Immobile smashed a volley past Consigli off a Sassuolo leg to double their lead five minutes later, and Frenchman Gregoire Defrel hit a consolation goal just before the hour for Sassuolo.
Inter Milan, meanwhile, remain below mid-table, 13 points behind Juventus, after Fabio Quagliarella's first-half strike secured a 1-0 win for Sampdoria in Genoa.