(CNN) -- Defending champions Inter Milan face the prospect of losing the Italian league lead to their bitter city rivals after being held 1-1 by Palermo in Sicily on Saturday evening.
Jose Mourinho's team could not reproduce the form that saw them so convincingly knock his former team Chelsea out of the Champions League on Tuesday.
Inter moved two points clear of second-placed AC Milan, who can go top of Serie A for the first time this season with victory against Napoli on Sunday.
The Nerazzuri took the lead after only 11 minutes against Palermo, with Argentina forward Diego Milito scoring a penalty after Lucio was fouled by Cesare Bovo.
But Edison Cavani leveled just 13 minutes later after good work by Fabrizio Miccoli, earning a point that put Palermo two points ahead of Juventus in fourth place and extended their unbeaten home run to 23 matches.
Inter, who had a 10-point advantage over Milan earlier in the season, have now won just once in their last seven league matches.
Roma consolidated third in the table with a 4-2 win at home to Udinese, moving to within four points of Inter, who they face next weekend.
Montenegro striker Mirko Vucinic scored a hat-trick, with two goals in the final 25 minutes killing off the visitors after Antonio Di Natale had drawn them level with a second-half double.
Fiorentina moved to within a point of seventh-placed Genoa after crushing the Rossoblu 3-0 at home with goals from Mario Santana, Alberto Gilardino with a penalty and teenage substitute Khouma Babacar.