A double from Fiorentina's in-form Dusan Vlahovic ensured Lazio missed the chance to close the gap on the Serie A top four in a 2-0 loss.
Lazio revived their hopes of Champions League qualification and subjected AC Milan to a second consecutive Serie A defeat.
Napoli won a 5-2 thriller against top-four rivals Lazio on Thursday to stay within touching distance of the Champions League places in Serie A.
Lazio president Claudio Lotito was banned for seven months and the Serie A club fined €150,000 ($176,925) by a national federal court.
Italian football was in mourning on Thursday following the death of Lazio youth player Daniel Guerini.
The great-grandson of Italian fascist dictator Benito Mussolini has signed his first professional contract with Serie A team Lazio.
Holders Bayern Munich booked their place in the Champions League quarterfinals with a professional performance to beat Lazio 2-1.
Lazio women's boss Carolina Morace has said Italy is "racist and homophobic" and the selection process stops women from managing men's teams.
Two goals from Alvaro Morata helped Juventus come from behind to beat Lazio 3-1 in Serie A on Saturday, closing the gap on leaders Inter Milan.