(Reuters) - Napoli substitute Dries Mertens scored a last-minute goal to salvage a 1-1 draw against AS Roma in Serie A on Sunday although they slipped further off the title pace as their 100 percent home record ended.
The Belgian volleyed the ball into the net from point-blank range after Jose Callejon mis-hit his shot from Lorenzo Insigne's pass to earn a point for his second-placed side.
Stephan El Shaarawy had given Roma a 14th minute lead, turning the ball into the net from six metres after Cengiz Under's pass from the byline evaded several players.
Roma's Edin Dzeko saw a shot cleared off the line by Raul Albiol before halftime and was also booked for diving.
"We didn't allow Roma to play the way they wanted, we put them under pressure and created chances," said Napoli coach Carlo Ancelotti, whose side had won their previous five games at the San Paolo this season in all competitions.
"We spent so much time in Roma's half but it wasn't easy to find space," he added.
Napoli, with captain Marek Hamsik equalling Giuseppe Bruscolotti's record of 511 appearances for the Naples club, dominated the second half and Callejon and Mertens both had goals disallowed for offside.
Napoli have now dropped six points behind leaders Juventus, who are chasing an eighth successive Italian title and won 2-1 at Empoli on Saturday with a Cristiano Ronaldo double.
Eighth-placed Roma have 15 points, level with AC Milan, Fiorentina, Sampdoria and Sassuolo.
Roma captain Daniele De Rossi made his 450th Serie A appearance for the club but limped off before halftime -- an injury which Roma coach Eusebio Di Francesco said affected his side after the break.
"De Rossi's absence penalised us," said Di Francesco, whose side have been frustratingly inconsistent this season. "It's disappointing to concede a goal in the last minute but Napoli deserved it.
"We have players who are still trying to absorb the tactical instructions and also the challenges of playing for a club like Roma. I thought we defended very well against a Napoli side in excellent shape."
(Writing by Brian Homewood; Editing by Ken Ferris)