Modest Udinese sold three of their best players before the season and never directly replaced them yet they could have been sitting in the Champions League qualifying round berth with just 10 games to go if they had weathered Napoli's late storm.
Midfielder Giampiero Pinzi grabbed a rare goal to put the hosts ahead in the first half in Udine before evergreen top scorer Antonio Di Natale hooked the ball over the line after Pinzi's second-half header had come off the post.
Udinese's Diego Fabbrini received a second booking in the 60th minute before Cavani missed an awful penalty and then scored a sublime free-kick for Napoli, knocked out of the Champions League last 16 by Chelsea in midweek.
Former Juventus defender Nicola Legrottaglie grabbed Catania's winner following a corner 11 minutes from time to shoot Vincenzo Montella's overachieving Sicilians up to joint-sixth.
"Now we can target new objectives, maybe even aiming at a European place," former Roma boss Montella told reporters.
"But let's leave the dreams to the fans. We have to stay realistic."
Lazio's defeat also meant leaders AC Milan and second-placed Juventus, who won 2-0 at Parma and 5-0 at Fiorentina respectively on Saturday, have almost unassailable cushions over the rest in the two automatic Champions League places.
Inter, dumped out of the Champions League by Olympique Marseille in midweek, have little hope of making next season's competition after Diego Milito missed a first-half penalty.
"I was talking to him about tactics," he said.
