Serie A leaders AC Milan slowed down their charge on the title after being held 0-0 by Lazio at home on Tuesday.
The host dominated throughout the game, but could not find way to break Lazio's stubborn defence, and had to settle for a scoreless draw after Zlatan Ibrahimovic hit both posts with a single shot.
Milan enlarged their lead at the top to five points but Napoli can narrow that to just two if they beat Chievo on Wednesday.
Lazio remain seven points adrift of the summit but could lose third place to either neighbours Roma or Inter Milan when they play their games.
The first half-sight of goal came on 27 minutes when Mathieu Flamini's wayward shot went to Ibrahimovic whose reaction header was woefully off target but hit a defender before going behind.
Lazio's best chance came when Milan centre-back Mario Yepes's defensive header landed on the top of his own goal.
On 34 minutes Ibrahimovic teed up Urby Emanuelson on a counter-attack but the Dutchman's finish was wild.
If the first half had been lacking in action, the first 10 minutes of the second quickly made up for it.
Ibrahimovic made space on the edge of the box and smacked a shot beyond Ferdinando Muslera but the ball ricocheted off both posts and back into the goalkeeper's grateful arms.
Flamini's cross-cum-shot was then held by Muslera before Ibrahimovic turned smartly but fired just beyond the far post.
Milan remained on top and were particularly dangerous on the counter with Robinho arriving on the overlap only to see Giuseppe Biava clear his goalbound shot off the line.
The hosts kept pushing but Lazio's gritty determination and resistance continued.
Four minutes from time Ibrahimovic again created space but Biava was there once more to block his shot before Emanuelson, who had an off-night in front of goal, fizzed the rebound well over.