Napoli are set to be without Faouzi Ghoulam for another extended period after the full-back suffered a suspected broken kneecap.
Ghoulam, 26, has been sidelined since the beginning of November after tearing the anterior cruciate knee ligament in his right knee.
And though he had returned to training, he suffered another setback in the same knee on Friday.
A club statement said: "Faouzi Ghoulam suffered a potentially serious knee injury in training in Castelvolturno on Friday. The early signs point to a fractured right kneecap.
"Ghoulam will be undergo tests to ascertain the extent of the injury at Villa Stuart today."
A key player in Napoli's rise to the top of the Serie A table earlier in the season, the left-back had reportedly interest from top Premier League clubs before his injury.
He signed a new contract with Napoli until 2022 in December.