Gonzalo Higuain scored again as Napoli came from behind to beat Empoli 5-1 on Sunday, ensuring his side remains top of Serie A and two points clear of title rival Juventus.
Juve won 4-0 at Chievo Verona, while Fiorentina stayed third despite a goalless draw at Genoa as fourth-place Inter Milan lost a heated derby 3-0 to AC Milan.
Inter striker Mauro Icardi missed a penalty with the score at 1-0 and the Rossoneri went on to claim only their second win in the past 10 derby matches.
"This is the greatest joy I've experienced since I've been coaching, because derbies won so roundly go down in history," said AC Milan boss Sinisa Mihajlovic, who wildly celebrated Inter's penalty miss.
"I even ripped my trousers at the knees, I was so happy because it was a decisive moment."
Mihajlovic spent two years at Inter as a player before retiring in 2006 and beginning his coaching career as assistant in Roberto Mancini's first spell in charge of the Nerazzurri.
His former boss was sent off five minutes into the second half for dissent and stuck up his middle finger to the Milan fans as he walked off.
"Yes I did it," Mancini said. "I showed my middle finger, some fans insulted me and they shouldn't have been there, seeing as there were stewards."
Torino's match against Hellas Verona ended 0-0, as did Udinese's against Lazio. Bologna squandered a two-goal lead but nevertheless beat Sampdoria 3-2.
Empoli took a surprise lead in Naples, in the 28th minute, when a well-worked free kick by Leandro Paredes took a deflection to wrongfoot Pepe Reina.
Its advantage lasted just five minutes before Higuain headed in Lorenzo Insigne's cross for his 22nd goal in 22 league matches this season.
Insigne completed the turnaround five minutes later, curling a stunning free kick into the top left corner.
Empoli debutant Michele Camporese turned into his own net shortly after the interval and Jose Callejon scored twice in the final 10 minutes.
Despite the win, Sarri needed no reminding about the title challenge facing his side.
"Juventus is clearly on another level," Sarri said. "We've found ourselves in this situation only because of their bad start. I don't know if Insigne and Higuain can close the gap to Juventus: we have great forwards but there's still a long way to go before we can match Juventus."
Juventus striker Alvaro Morata had broken a 20-match goalscoring drought with a double in the Italian Cup semifinal against Inter midweek and he scored another double in Verona.
The Spain forward netted his first in the sixth minute, prodding in Stephan Lichtsteiner's low cross at the back post, and doubled his tally five minutes before halftime with another tap in.
Alex Sandro and Paul Pogba sealed the win in the second half as Allegri matched Antonio Conte's all-time club record of 12 consecutive league victories.
"Perfection doesn't exist, but we're working on it," said Juventus coach Massimiliano Allegri said, who highlighted that "there are still 16 matches left ... We have to play against Genoa and Frosinone, which are two tricky matches, and then our direct battle against Napoli.
"The lads win the matches on the pitch, I don't care about records at all ... I would be upset if we won 20 matches in a row and then lost the title. What matters is winning the title."
The record winning streak in Serie A is Inter's 17-match run in 2006-07.
At San Siro, Inter goalkeeper Samir Handanovic had little to do for most of the opening stages of the match and was doing exercises shortly before the opening goal as he was the only player in his half.
Milan broke the deadlock in the 35th when Alex met Keisuke Honda's cross with a towering header. Coincidentally, Milan's pre-match choreography had depicted Mark Hateley's towering header in the 1984 derby.
Inter was awarded a penalty in the 69th when Alex brought down Icardi but the Inter substitute saw his spot kick come off the right upright.
Bacca doubled Milan's lead three minutes later, volleying in M'Baye Niang's cross from close range. Niang got on the scoresheet himself four minutes later, slotting home the rebound after Handanovic had saved his first attempt.
Mancini was unhappy about incidents involving Milan goalkeeper Gianluigi Donnarumma and Alex, and was critical of referee Antonio Domato.
"Donnarumma and Alex should have been sent off, Domato doesn't know the rules," Mancini said. "The referee and his assistants were a disaster, they were the worst on the pitch.
"We had a great first half, in which at least one of their players should have been sent off," he added. "We deserved to finish the first half ahead, not behind."