Left-back: Aleksandr Kolarov
Statistically the most prolific fullback last season in Europe, Kolarov is yet to hit those heights this term, but that isn't to suggest he's been bad. Kolarov has already netted twice in the league and also created a handful of good chances.
He was the best player for Serbia at the World Cup, and with time, would surely be back to his marauding best.
Centre-back: Kalidou Koulibaly
The Senegalese defender is an underrated player, but quiet the ace in Serie A. He's been the defensive rock in this Napoli side for the last four years now and has played an important role in helping keep four clean sheets this term.
His ability to sniff out danger has averaged 3.1 clearances while also making 1.8 tackles per game. Koulibaly could once again prove to be a tough nut for Roma to crack.
Centre-back: Kostas Manolas
Manolas is an all-action defender: he tackles, he charges out of his zone, he pops up with important goals (howdy, Barcelona?), and he also lays assists sometimes. The Greek centre-back looked out of sorts amid Roma's erratic run this term but is slowly getting back to his best.
And the timing couldn't have been more perfect. His defensive nous would be crucial against an attacking side like Napoli, while his interventions at the other end, during set-pieces, can come handy too.
Right-back: Alessandro Florenzi
A midfielder by trade, Florenzi has been operating from the fullback position for quiet sometime and seems to be at home as a right-back. This season, he's already scored and assisted once each, while defensively too, he has been one of the better players for the Giallorossis.
His crosses have improved and ability to pick out passes from the right has added a new dimension to Roma's attack.