Roma head coach Jose Mourinho has congratulated Napoli on already wrapping up the Serie A title, despite the season only being halfway complete.

Napoli are 12 points clear of closest challengers Milan at the summit after winning 16 of their opening 19 games and losing just once.

They are just the third different team in Serie A history, after Juventus three times and Inter once, to have won that number of games in the first half of a season.

Roma will look to halt Napoli's momentum at Stadio Diego Armando Maradona on Sunday, but regardless of the result, Mourinho can only see one outcome in the title race.

"I'll say what I always say: they have already won the Scudetto, and deservedly so," Mourinho said at Saturday's pre-match press conference.

"They are an excellent team, with an excellent coach in Luciano Spalletti. They are now 12 points ahead and there are no teams that scare them. The Scudetto is theirs.

"We won't just step out of the way for them, but they have already won the championship. Congratulations to them."

Napoli are unbeaten in eight of their past nine Serie A matches against Roma, with their sole defeat in that run coming in November 2019 (a 2-1 loss at Stadio Olimpico).

Among the 10 coaches Mourinho has faced at least four times in Serie A, Spalletti is the one he has the worst win percentage against (20 per cent), with just one win from five.

For Spalletti, though, it is still a case of one game at a time as Napoli target an elusive first title since the 1989-1990 season in the days of Diego Maradona.

"The results of other teams is not down to us, so we must therefore always behave the same and play well, while also being humble," Spalletti told reporters.

"We pay attention to taking it one step at a time, concentrating on where we put our feet. We work daily and never beyond."

Napoli are unbeaten in their past four home league games against Roma – not since between 1985 and 1989 have they enjoyed a longer such streak (a run of seven).