Juventus dominated but was held to 0-0 by Lazio in Serie A on Saturday, just three days before its key Champions League match against Chelsea.
Leonardo Bonucci hit the crossbar for Juventus but the defending champion — which had scored 10 goals in its previous two matches — could not find a way past Lazio goalkeeper Federico Marchetti.
Marchetti pulled off a spectacular stop, changing direction midair to keep out Arturo Vidal's deflected effort. Sebastian Giovinco also went close on several occasions for Juventus, who clearly missed the suspended Andrea Pirlo.
"We had so many scoring opportunities and dominated the match, it's a pity we didn't get the goal," Juventus assistant coach Angelo Alessio said. "Lazio played in a catenaccio style and were simply defensive throughout; we even hit the crossbar, if we had scored once it could have finished in a thrashing.
"If you don't score, you don't win, it's simple. But there are only positives to take from tonight."
Lazio didn't have a shot on target in the entire match and struggled to get out of its own half.
"Congratulations to Juventus," Lazio coach Vladimir Petkovic said. "We tried to play but they were too strong and kept on pressing, they trapped us in the area. We have to thank our goalkeeper that it ended 0-0.
"At least tonight we can say we didn't concede, lately we've conceded quite a lot. But up front we didn't have any courage or initiative. However, the point is still good for morale and the standings."
Juventus extended its lead in the standings to five points over Inter Milan, which plays Cagliari on Sunday.
It remains five points above Napoli which let slip a two-goal lead to draw 2-2 at home to AC Milan. Stephen El Shaarawy scored both Milan goals to reaffirm his status as Italy's in-form striker.
Juventus decided against resting players ahead of the Chelsea match but was without key playmaker Pirlo, as well as Mirko Vucinic, who was a late withdrawal from the squad with flu.
However, Paul Pogba returned after being suspended by coach Antonio Conte last weekend for showing up late to training twice.
Lazio beat Roma last weekend to snap a run of three league games without a win, but has not beaten Juventus in nearly nine years. Captain Stefano Mauri and Senad Lulic were banned.
Juve went close in the 19th when Marchetti did well to parry Giovinco's shot at full stretch and Fabio Quagliarella hit the rebound into the side netting.
Marchetti performed a sensational save on the hour. Vidal's long-range shot was deflected by Quagliarella, but Marchetti managed to change direction to tip it over the crossbar.
The Lazio goalkeeper was finally beaten in the 75th but Bonucci's shot following a corner smacked off the crossbar.
In Naples, two defensive blunders helped Napoli establish a two-goal lead.
Gokhan Inler scored his first goal for Napoli in the fifth minute with a swerving, long-range effort which wrong-footed Milan goalkeeper Christian Abbiati, who was captain for the night in place of the suspended Massimo Ambrosini.
Napoli doubled its lead on the half hour when Lorenzo Insigne's shot took a slight deflection off Francesco Acerbi and sailed through Abbiati's legs.
It was almost worse for Milan moments later. Inisgne pounced on a terrible backpass from Kevin Constant but rather than going for goal passed to Edinson Cavani, and the danger was cleared by a last-ditch tackle from Philippe Mexes.
Milan pulled one back on the stroke of halftime when Mattia De Sciglio cut the ball back to El Shaarawy, who sent a looping effort in from the edge of the area.
Napoli had several chances to extend its lead but Milan completed its comeback eight minutes from time when Robinho sent a through ball in for El Shaarawy to side-foot it home for his 10th goal of the season.
"I dedicate the goals to my teammates who gave their all and especially to Christian, who made a mistake," El Shaarawy said. "He has saved us so many times.
"We played a great game and are happy with the comeback. I think this was one of our best performances of the season. The [club] president [Silvio Berlusconi] gave us an extra push [with his visit on Friday]."