There was a 30-minute half-time break because of a thunderstorm in the Inter Milan v Torino match
Inter Milan closed the gap on Napoli to one point by beating Torino on Sunday, while the Serie A leaders were held at home by Genoa.
Inter's game in Turin had to be halted because of a medical emergency early in the first half and was then further delayed by a thunderstorm.
Inter took the lead in spectacular style with Nicola Zalewski's superb 25-yard strike.
But a sudden downpour led to puddles appearing on the pitch and left the ball unable to bounce on the surface. The half-time interval was extended to 30 minutes in an effort to let the water drain off the pitch.
Following an inspection by referee Federico La Penna, the game was able to resume and in the 49th minute, with the rain still coming down, Inter were awarded a penalty after Torino keeper Vanja Milinkovic-Savic fouled Mehdi Taremi.
Kristjan Asllani converted from the spot to double the visitors' lead and seal the victory.
As the heavy rain began to ease, Inter pushed forward with greater intensity and only a series of sharp saves from Milinkovic-Savic prevented them from adding a third.
Adam Masina found the net for Torino with a spectacular overhead kick deep into time added on, but the goal was ruled out after he was adjudged to have muscled Asllani out of the way to make room for the effort.
The result ended an excellent week for Inter Milan who defeated Barcelona 4-3 last Tuesday to win an epic Champions League semi-final 7-6 on aggregate.
Leaders Napoli drop two points at home
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That result briefly left Inter tied on 77 points with Napoli.
But, in the late match, Napoli drew 2-2 at home to Genoa to move one point clear with two matches remaining.
Former Inter striker Romelu Lukaku put Napoli ahead before an own goal from Alex Meret made it 1-1. Giacomo Raspadori restored Napoli's advantage midway through the second half only for Johan Vasquez to equalise.
Napoli will win Serie A for only the fourth time, but for the second time in three years, if they win their last two matches - away at Parma on Sunday, 18 May and then at home to Cagliari seven days later.
If Napoli and Inter finish level on points then the two will have a title-deciding play-off to find out who will be champions.
