Roma coach Luciano Spalletti all but threw in the towel to Serie A title rivals Juventus following Saturday's 2-1 defeat to Napoli.

Makeshift Napoli striker Dries Mertens hit a brace in a thrilling victory at the Stadio Olimpico which, should Juventus beat Udinese away on Sunday, would leave Roma 10 points adrift in second place.

Although the capital club still have a mathematical chance of catching the champions over the remaining 11 games, Spalletti told Sky Sport that a sixth successive title was now in the bag for Juve.

"We have to be realistic. For us it's now almost impossible to catch Juventus," he said.

Belgium midfielder Mertens was given the nod ahead of striker Arkadiusz Milik despite the Poland star's recent return from a five-month injury lay-off.

And coach Maurizio Sarri's intuition proved right ahead of an entertaining encounter that saw Napoli soak up long spells of pressure before Mertens exposed gaping holes in the Roma defence.

Napoli took a 1-0 lead into half-time after Mertens struck against the run of play to flick the ball over onrushing goalkeeper Wojciech Szczesny on 26 minutes.

Mertens completed added his second, taking his league tally for the season to 18 goals, five minutes into the second half with another cool finish following Lorenzo Insigne's inswinging cross towards the back post.

When Kevin Strootman reduced the arrears on 89 minutes it sparked a dramatic late rally from Roma that saw Pepe Reina acrobatically palm a drive off the crossbar before clearing with his leg.

But Napoli, who saw Sarri sent to the stands for dissent midway through the second period, held on for a valuable win.

After virtually dropping out of title contention last week following a 2-0 defeat to Atalanta which left them trailing Juventus by 12 points, Napoli are now just two points behind Spalletti's men in the race for the second automatic Champions League spot.

Napoli maintained their media blackout, imposed two weeks ago following club president Aurelio De Laureniis's public criticism of their performance in a 3-1 Champions League defeat to Real Madrid.

Roma midfielder Diego Perotti admitted Napoli were deserving winners but said his side still had the advantage in the battle for second place.

"We almost came back to grab a draw but they were better than us," he told Premium Sport.

"Today we played badly but we're in front of them (in the table) and we haven't said our last word yet."