Rossi is in the USA to have the injury assessed.
"Before going to Colorado, where I will see the Professor who operated on my knee in the past, I want to thank everyone for their messages of respect and affection," wrote Rossi on his official website.
"These have been difficult and painful hours, but the messages and the support of everyone moved me and filled me with pride.
"I thank all of Florence, the club and my teammates... I thank all the Italian fans and all the colleagues from other teams who had kind words for me.
"Thank you all from the heart. We'll see each other soon!"
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball