Napoli failed to mathematically secure third spot in Serie A as it was held to an entertaining 0-0 draw at Inter Milan on Saturday.
Ealier, Fiorentina crushed relegation-threatened Bologna 3-0 to keep alive its faint hopes of snatching the final Champions League berth from Napoli.
Fiorentina moved to eight points behind Napoli with three rounds remaining. The two meet in the Italian Cup final next Saturday.
Napoli star striker Gonzalo Higuain faces a race to be fit in time after being taken off on a stretcher four minutes from time following a tackle on Marco Andreolli.
The Argentina forward, who has 20 goals in all competitions this season, has heavy bruising on his ankle but his World Cup hope is not at risk.
"It's a good result, but we could have won this match," Napoli coach Rafael Benitez said.
"Higuain has heavy bruising and we have to evaluate his injury. We still don't know, the doctor isn't saying anything more, at least not for now."
Both managers were facing former teams at San Siro as Walter Mazzarri coached Napoli for four years before moving to Inter last summer. It was Benitez's first match at Inter since his dismissal in December 2010 following a brief tenure.
"In the first half we played a great game," Mazzarri said. "We suffered a bit with their counterattacks, but we would have deserved a goal. In the second half we lacked strength. It's a pity, we could have won if we had managed to score in the first half."
Both teams enjoyed numerous opportunities but couldn't score. Gokhan Inler went closest with an effort which crashed off the right post eight minutes from time for Napoli.
There was controversy in the first half as Palacio fell under a tackle from Miguel Britos as he was about to burst into the box but the referee flashed only a yellow card with Inter players and fans calling for a red.
Inter remained fifth, four points behind Fiorentina, which is all but mathematically sure of a Europa League spot next season after Juan Cuadrado's brace.
Bologna started brightly but Fiorentina began to get into the game and broke the deadlock in the 22nd minute when Cuadrado volleyed home Joaquin's low cross at the far post.
Josip Ilicic doubled Fiorentina's lead 12 minutes later with a 25-meter effort, which took a deflection off Michele Pazienza to loop over Gianluca Curci.
Cuadrado sealed the result three minutes from time as he raced past his marker before unleashing a rocket from outside the area.