Napoli dropped points for only the second time this season in the league when they were held 0-0 at Chievo on Sunday and Juventus cut the gap to one point with a 2-1 win over bottom club Benevento.
Coach Maurizio Sarri said his team lacked sharpness after facing Manchester City in the Champions League four days earlier, reinforcing the widely-raised doubts over whether his squad has the strength in depth for both a European and domestic campaign.
"We got to the end of a difficult run of games and we were rather weary, we lacked sharpness," said Sarri.
He also admitted that they missed left back Faouzi Ghoulam who is expected to be out for several months with a knee injury.
Ghoulam, regarded as one of Sarri's most important players, was replaced by Mario Rui who found the Algerian a tough act to follow on his first start for Napoli.
"Of course, we missed Ghoulam's strength and running but Mario is the one who is playing now and we have to get him up to 100 percent," said Sarri.
"Mario Rui did quite well, considering that it was only his third match in five-and-a-half months," he added.
With Poland forward Arkadiusz Milik also out with a knee injury, Napoli's squad is likely to be severely tested once the league resumes following the international break.
"This is the situation we are in and we have to do the best we can with the squad at our disposal," said Sarri.
Napoli have delighted the public with their slick attacking football over the last year, but Sarri suggested that they needed to learn how to win without playing at full steam.
"We need to start winning matches where we don't play brilliantly and, in this sense, missing two important players like Milik and Ghoulam represents a problem," he said.
(Writing by Brian Homewood in Bern; editing by Amlan Chakraborty)
