Rossi limped off with a muscular problem after just 37 minutes.
Viola coach Vincenzo Montella said: "I haven't spoken to him yet, but we'll run the tests tomorrow and see. It's a shame, as he was in great shape. I was already thinking of not taking him to Ukraine against Dnipro in the Europa League, but now that decision has been forced upon me."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball