Krasic rescues Juventus at Catania
The two sides share the lead with eight points from four games. Atalanta remain the only other unbeaten team after a 2-1 win over Novara.
Promoted Atalanta, who won with goals from Matias Schelotto and Luca Cigarini, have the best playing record with three wins and a draw.
However they have only four points after having six deducted before the start of the season in a Serie B match-fixing scandal.
Genoa's unbeaten record ended when they lost 2-1 at Chievo, who also beat Napoli in midweek.
Striker Rodrigo Palacio, recalled by Argentina last week after a three-year absence, put Genoa ahead just after halftime with his fourth goal in as many games.
Sergio Pellisier levelled for Chievo in the 74th minute and Davide Moscardelli scored a stoppage-time winner.
Siena beat Lecce 3-0 helped by a brace from Emanuele Calaio after Mattia Destro opened the scoring while Lazio and Palermo played out a goalless draw in the afternoon's other game.
Juventus fell behind after 21 minutes at Catania, Alejandro Gomez supplying a low cross which was turned into the net by his fellow Argentine Gonzalo Bergessio.
Serbian striker Krasic equalised four minutes after the re-start with a right-foot shot which was badly misjudged by goalkeeper Mariano Andujar, another member of the Argentine contingent in the Sicilian side.
Juve had a let-off late in the game when a mistake by Giorgio Chiellini set up a chance for David Suazo but the Honduran was foiled by Gianluigi Buffon