Race leader Alberto Contador was caught up in a crash in the frantic sprint finish of the sixth stage of the Giro d'Italia on Thursday as Germany's Andre Greipel claimed victory.
Greipel (Lotto-Soudal) won the 183-kilometre route from Montecatini Terme to Castiglione della Pescaia ahead of Matteo Pelucchi (IAM Cycling) and Sacha Modolo (Lampre-Merida).
Contador (Tinkoff-Saxo), who assumed the maglia rosa on Wednesday, remained two seconds clear of Fabio Aru (Astana) and 20 seconds clear of Team Sky's Richie Porte.
But the Spaniard, who responded from crashing out of the 2014 Tour de France by winning the Vuelta a Espana, was unable to put on the race leader's pink jersey at the podium presentation, leading to doubts over his condition.
A medical bulletin from the race organisers later revealed Contador underwent an X-ray and scans of his left shoulder.
The bulletin read: "Clinical examination revealed a slight instability of the left shoulder joint, as compared to the right one. The rider experienced slight pain."
Asked if it was possible Contador might not start on Friday, Feltrin said: "Yes, it is possible. In the morning, when we have reliable information, we'll decide what to do."
