Genoa coach Gian Piero Gasperini said he could hardly believe the Serie A table after his unheralded side beat Milan 1-0, ensuring they would finish the weekend in third place.
Luca Antonelli headed the only goal from a corner in the 32nd minute, scoring for the third game in a row, as Genoa won for the seventh time in 14 Serie A games this season.
"When I look at the table, I'm in disbelief," Gasperini told Sky Sport Italia. "However, we've earned and deserve every point."
Genoa, who have 26 points, won the last of their eight Italian titles in 1924 and finished 14th last term, having narrowly avoided relegation in the two seasons before that.
Napoli dropped two points behind Genoa in fourth after a 2-2 at home to promoted Empoli, who took a 2-0 lead with goals from Simone Verdi and Daniele Rugani.
Napoli replied with two goals in five minutes as Duvan Zapata headed in from a corner and Jonathan De Guzman scored with a low shot after Christian Maggio's centre was deflected into his path.
Lazio sent table-propping Parma to their fourth straight loss, and their 12th in 14 games, as they won 2-1 at the Tardini stadium.
Atalanta, who had only mustered five goals in their first 13 matches, scored three in eight minutes either side of halftime as they came from behind to beat Cesena 3-2.
In the late game, former Inter coach Andrea Stramaccioni returned to San Siro to lead his Udinese side to a 2-1 victory.
After being sacked in May 2013, the young tactician took a year out before landing the Bianconeri job and his one-time employers will wonder what might have been after watching Udinese dominate proceedings in Milan.
Mauro Icardi gave Inter the lead just before half-time but a sumptuous solo goal from Bruno Fernandes drew Udinese level before substitute Cyril Thereau capitalised on a defensive blunder to steer home the winner.
Stramaccioni's men climb to eighth in the table after snapping a five-match winless streak while Roberto Mancini's Inter are marooned in the bottom half having endured their fifth defeat of the campaign.