Claudio Marchisio blew open the Serie A title race when his superb goal gave 10-man Juventus a 2-1 win over leaders Inter Milan in an enthralling game on Saturday.
Inter's lead has been cut to four points after second-placed AC Milan outclassed Sampdoria 3-0 at the San Siro while third-placed Juve are a point further back after 15 matches.
Italy midfielder Marchisio danced past Walter Samuel and dinked the ball over Inter goalkeeper Julio Cesar just before the hour mark to inflict Inter's second league defeat this term.
Champions Inter, aiming for a fifth straight scudetto come May, were largely on top when Marchisio struck having equalised after 26 minutes when a completely unmarked Samuel Eto'o nodded in Dejan Stankovic's cross after a quick free-kick.
The Cameroon striker has failed to really shine since his July swap move from Barcelona involving Zlatan Ibrahimovic, but he was busy throughout at Turin's Stadio Olimpico.
Juve had taken the lead after 20 minutes when Diego's free kick was headed on by Giorgio Chiellini, wearing a mask because of a broken nose, and the ball deflected in off Inter's Lucio.
Inter coach Jose Mourinho sarcastically applauded the referee after the goal for awarding the free-kick and was immediately ordered to the stands.
The match was suitably tough-tackling and the atmosphere electric for one of Serie A's biggest rivalries but fears Juve fans would again consistently racially abuse Inter's black striker Mario Balotelli failed to materialise.
Juve were forced to play a game behind closed doors last term after supporters sang racist chants towards Balotelli and the authorities had said the game would be suspended if there was more racial abuse on Saturday.
Balotelli was only whistled when he came on after an hour and again was booed after two theatrical falls, one of which led to Felipe Melo's dismissal late on for a second booking following a brawl.
Earlier, in-form AC Milan scored three goals in the first 23 minutes to seal an easy victory over faltering Sampdoria.
Ronaldinho set up the first two goals but then went off with a minor hamstring strain with one eye on Tuesday's Champions League clash at FC Zurich, where a win will put Milan through.
Striker Marco Borriello headed in the Brazilian's cross after just two minutes for his fourth league goal of the season.
Ronaldinho, thriving on the left of a new three-man attack, then laid the ball off for midfielder Clarence Seedorf to smash in his 5Oth Serie A goal from just inside the box after 21 minutes.
Alexandre Pato tapped the ball in on the rebound soon after to secure a fifth straight league win for Leonardo's side, who have recovered from a shaky start to the campaign.
Sampdoria, beaten by Genoa in last weekend's derby and by Livorno in the Italian Cup in midweek, have suffered a drastic dip in form having been early season leaders, with playmaker Antonio Cassano again quiet at the San Siro.