Napoli are concerned that Mathias Olivera has sustained a very serious injury after he was stretchered off in tears during the game with Atalanta.
The left-back had been running without any opponents nearby when he suddenly slipped and badly sprained his left knee.
It became immediately clear that this was a bad injury and he was strapped to a stretcher, carried off in tears at the Gewiss Stadium in Bergamo.
This is a further concern for new coach Walter Mazzarri, who just took over from sacked Rudi Garcia during the break for international duty, because there are now no left-backs available.
Mario Rui is already on the treatment table with a thigh strain and he is not expected back until at least mid-December.
Juan Jesus is having to fill in on the left of defence during the rest of the Serie A game with Atalanta, but this is a problem going into Tuesday’s Champions League clash with Real Madrid.
Atalanta wing-back Davide Zappacosta also limped off during this match, having sprained his ankle.