Juventus' 12-match winning Serie A run was snapped on Saturday when they were held 1-1 by Lazio at the Roma Olimpico Stadio on Saturday.
Napoli also had a difficult match as they managed to scored two minutes from end to get a 1-1 draw at home against Chievo.
Juventus, who have not tasted defeat in Serie A since a 4-2 defeat at Fiorentina in October, suddenly faced an uphill battle at the 25th minute when their goalkeeper Gianluigi Buffon was dispelled for bringing down Miroslav Klose in the area.
Antonio Candreva converted the resulting penalty to award a 1-0 lead to Lazio, who have not beaten Juventus in the league since December 2003.
Juventus did not appear to be hindered by the dismissal, however, and they continued to dominate the tempo.
The reigning champions were rewarded on the hour mark when a superb move was finished by Fernando Llorente's looping header from Stephan Lichtsteiner's pin-point cross.
Lazio head coach Edy Reja said his side could have beaten Juventus as they were unlucky in the draw with the 10-man Serie A leaders.
"We had a terrible start and were we were slightly nervous under their pressing for 20 minutes. We did better, were a little unlucky to hit the woodwork twice, as we could've won," he said.
His Juventus counterpart Antonio Conte said the draw proved his side's title credentials.
"We picked up a point and I think the team proved again tonight why they are top of the table. Juventus never gave in, continued to play football and trying to win the game despite going down to 10 men," he said.
Earlier on Saturday, Napoli's fading title hopes were dealt another blow as they were held by strugglers Chievo.
The Flying Donkeys took a surprise lead after 18 minutes via a superb driven half-volley from Gennaro Sardo.
Napoli's relentless pressure finally paid off in the 88th minute when Raul Albiol drove a half-volley into the floor that bounced into the bottom corner.
Rafael Benitez's men should have equalized in the 25th minute when Jose Callejon's ball across the face of goal was inexplicably put wide by Gonzalo Higuain at the back post with the goal gaping.
Dries Mertens also went close when his effort from an acute angle struck the outside of the post.
Benitez said his side Napoli were very unlucky to hit the woodwork three times.
"We needed a bit more speed in moving the ball, but hitting the woodwork three times against a clammed-up team was very unlucky," he said.
Chievo head coach Eugenio Corini said he was disappointed with the result.
"We had two or three good chances to double our lead, even if obviously in the second half Napoli pegged us back more," he said.
The result means that Napoli remain third and 12 points behind leaders Juventus, while Chievo are just one point above the relegation zone in 16th.
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