Fiorentina saw their 2-1 first-leg lead evaporate on Tuesday as they were beaten 3-0 by Juventus in Florence while Rafael Benitez's side fell to a 1-0 defeat against Lazio a day later.
Napli's loss angered president Aurelio De Laurentiis, who later threatened the club's players with a post-season training retreat if results do not improve.
Both clubs now have just the UEFA Europa League and a continental push in Serie A to focus on, with the sides in the running for a top-five spot.
Just two points separate Fiorentina in fourth and Napoli in sixth, with Benitez urging his players to be more clinical.
"All I can do is analyse everything that has happened on the pitch, and sometimes you do not get the goals you deserve and that has happened to us," he told reporters after the Lazio game.
"There's no point in dwelling on this result. The team created so many chances and the players showed they are alive and capable of playing an attacking game.
"And we hope that in future we can be more effective in front of the opposition's goal."
Champions Juventus have fitness doubts over their in-form striker Carlos Tevez ahead of Saturday's trip to bottom side Parma, who picked up a rare victory on Wednesday against Udinese.
Juve appear certain to take maximum points against Serie A's crisis club meaning Roma can ill afford any slip-ups in their bid to keep alive any faint hopes of reeling the runaway leaders in.
Rudi Garcia's side travel to Torino equally aware of the threat from third-placed rivals Lazio, whose seven-match winning run in the league will be tested by Empoli.
With relegation candidates Cesena and Cagliari facing Chievo and Genoa respectively, Atalanta have a big opportunity to put further daylight between themselves and the bottom three.
However, Atalanta boss Edy Reja will be without striker Mauricio Pinilla who begins his three-match suspension for an off-the-ball incident with Migjen Basha in the defeat to Torino last time out.
A resurgent Milan can take a big step forward in their bid for a European spot when they host fifth-place Sampdoria on Sunday, while stuttering Inter travel to Verona.
Neither Udinese nor Palermo boast strong form going into Sunday's clash at the Stadio Communale Friuli, although both appear safe from the drop going into the run-in.
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