Inter Milan missed the chance to go three points clear at the top of the table after they were held to a 1-1 draw by Atalanta at Stadio Giuseppe Meazza.
Lautaro Martinez grabbed an early lead for Inter in the fourth minute but Robin Gosens snatched the equaliser for Atalanta with 15 minutes remaining.
The visitors had a big opportunity to snatch a late victory in the last two minutes after they were awarded a penalty but Luis Muriel's spot-kick was saved by Inter goalkeeper Samir Muriel.
Antonio Conte's charges lead the table by only a point and they could lose their top spot if Juventus beat Roma on Sunday evening while Atalanta remain in fifth place with 35 points after 19 games.
Zlatan Ibrahimovic scored his first goal since his return to AC Milan, who got back to winning ways with a 2-0 victory over Cagliari at Sardegna Arena.
Rafael Leao opened the scoring for the Rossoneri a minute after the break while Ibrahimovic made the three points safe with the second goal in the 64th minute.
The victory lifted Milan up to eighth on the table while Cagliari remain in sixth place.
Lazio clinched a club record tenth consecutive victory in Serie A with a 1-0 win over Napoli at Stadio Olimpico.
The hosts got the breakthrough with eight minutes remaining after Napoli goalkeeper David Ospina gave away possession cheaply inside his own box to Ciro Immobile, who netted his 20th goal of the season.
Lazio remain in third place on the log with, just three points behind second-placed Juventus while Gennaro Gattuso's charges dropped to tenth.