* Fiorentina lose 100 percent record in draw with Cagliari
* Gomez suffers knee injury (Updates with Sampdoria-Genoa, paragraphs 4-5)
Sept 15 (Reuters) - Fiorentina conceded a late goal, had David Pizarro sent off and lost their 100 percent Serie A record in a 1-1 draw at home to Cagliari on Sunday, with an injury to Mario Gomez compounding their frustration.
Germany forward Gomez suffered a partial tear to the medial collateral ligament in his right knee after colliding with Cagliari goalkeeper Michael Agazzi as he shot wide of the goal from six metres.
Antonio Di Natale celebrated his 300th Serie A appearance for Udinese by scoring a late equaliser in a 1-1 draw at home to Bologna and Lazio efficiently swept aside Chievo 3-0 with three first-half goals.
Genoa outclassed neighbours Sampdoria to win their derby 3-0 and pick up their first points of the season.
Luca Antonini's ninth-minute opener was followed by second-half goals from Emanuele Calaio and Francesco Lodi, who curled in an exquisite free kick which prompted coach Fabio Liverani to run on to the pitch and join the celebrations.
Fiorentina, who dominated most of their match but struggled to find a way past a well-organised Cagliari defence, finally broke through in the 71st minute when Borja Valero headed in Giuseppe Rossi's cross from close range.
The Sardinians, however, had looked dangerous throughout the second half and equalised in the 89th minute when Chilean forward Mauricio Pinilla, a second-half substitute, headed in Victor Ibarbo's cross from the right.
Fiorentina had a penalty appeal turned down in stoppage time when Rossi went down under a challenge and Pizarro, who had been on the pitch for 20 minutes, was shown a second yellow card for dissent.
"I can accept technical mistakes but I don't accept it when referees fail to judge the players' behaviour in a uniform manner," said Fiorentina coach Vicenzo Montella.
"Other players were saying much worse things and that's what I told the referee at the end.
"Tactically, it was a very good game but Pinilla's goal was a shame because Cagliari were not creating anything at that point in the match."
The draw left Fiorentina level with Inter Milan and Juventus on seven points from three games, two behind Napoli who have won all three games. Cagliari have four points.
Lazio, Livorno and Hellas Verona all won at home to move on to six points from three games.
Lazio created three goalscoring chances in the first half and converted them all, through Antonio Candreva, Luis Cavanda and Senad Lulic, at a half-empty and rain-lashed Stadio Olimpico.
Two goals from Brazilian forward Paulinho gave promoted Livorno a 2-0 win over Catania, while his compatriots Raphael Martinho and Romulo scored in each half as Hellas Verona beat Sassuolo 2-0 in a battle of two promoted sides.
Alessandro Diamanti's superb free kick put Bologna ahead midway through the second half at Udinese but 35-year-old Di Natale was not to be outdone, volleying home after Luis Muriel skipped between three defenders and chipped the ball to him.
(Writing by Brian Homewood in Berne; Editing by Clare Fallon and Sonia Oxley)