Napoli sit second at four points behind leaders Juventus and face their first big test since Milik was sidelined for up to six months.
A crushing knee injury to Poland striker Arkadiusz Milik paves the way for substitute Manolo Gabbiadini to lead Napoli's Serie A title challenge, according to Italian goalkeeping legend Dino Zoff.
Napoli sit second at four points behind leaders Juventus and face their first big test since Milik was sidelined for up to six months with a cruciate ligament injury, when they host Roma on Saturday.
With Juve hosting struggling Udinese in Turin, Napoli can ill afford to drop points against an ambitious Roma side that sits just a point further behind.
Gabbiadini was left frustrated many times this season as he sat on the bench while Milik, a direct replacement for Juventus-bound striker Gonzalo Higuain, hit four goals in seven league games and three in just two Champions League outings.
But Italy legend Zoff, the Napoli goalkeeper for five seasons before a 1972 move to Juventus, told Corriere della Sera: "If Gabbiadini, as I believe he can, steps in to replace Milik then Napoli can relaunch the title race.
"Four points is a lot, but not much either. We'll see what happens this October, it could be decisive."
Flanked by Dries Mertens and Jose Callejon in Sarri's trademark 4-3-3, it remains to be seen how Gabbiadini fares. While Milik is notably lethal in and around the area, Gabbiadini is a far more versatile forward with a liking for cutting in from the right to shoot with his left.
Yet his chance of making an immediate impact could be boosted by Roma's current bout of travel sickness.
Luciano Spalletti's men have yet to win away in three attempts, their last a humbling 3-1 defeat at Torino a fortnight ago.
Club icon Francesco Totti was quick to wish Milik a "speedy recovery", but said: "Napoli are just as strong" without him. "I expect a very difficult game."
Ancelotti, a former Roma striker before beginning a successful coaching career with some of the world's biggest clubs, indicated midweek the Giallorossi would be a match for the hosts.
"Napoli are better in possession, Roma are deadly when they get it forward quickly," Ancelotti he told Il Messaggero.
Yet the odds are on a Napoli win and Roma slipping further off the pace of Juve, who are not expected to slip at home to a Udinese side struggling in 16th with only seven points in as many games.
Juve coach Massimiliano Allegri should be able to rest Higuain ahead of next week's Champions League trip to Lyon, where a win would cement the Italians' grip on Group H.
He could also welcome midfielder Claudio Marchisio back from a six-month injury absence after he confirmed his fitness with a goal in a 2-0 friendly win over lower league side Pro Eureka Settimo in midweek.
Reports said Marchisio, who ruptured his crucial anterior ligament in his left knee on April 17, will be a second-half substitute.
Elsewhere, Lazio host Bologna looking to maintain a strong start that has seen Simone Inzaghi's men up to fourth, behind Roma only on goals difference.
Fellow surprise packages Chievo, also on 13 points, beat Inter Milan on the opening day of the season and are hoping to complete the Milan double when Vincenzo Montella's AC Milan visit on Sunday.
Inter coach Frank De Boer, meanwhile, has left doubts hanging over embattled midfield pair Marcelo Brozovic and Geoffrey Kondogbia ahead of Cagliari's visit on Sunday.
Croatia international Brozovic has been sidelined after falling foul of De Boer's strict disciplinary approach, while Kondogbia was unceremoniously hauled off after 28 minutes of a 1-1 home draw with Bologna last month for "failing to listen to instructions".
"I don't know yet," was De Boer's reply when asked if either player would feature.
Napoli v Roma (1300 GMT), Pescara v Sampdoria (1600 GMT), Juventus v Udinese (1845 GMT)
Fiorentina v Atalanta (1030 GMT), Genoa v Empoli (1300 GMT), Inter Milan v Cagliari (1300 GMT), Lazio v Bologna (1300 GMT), Sassuolo v Crotone (1300 GMT), Chievo v AC Milan (1845 GMT)
Palermo v Torino (1845 GMT)