"From all of the Isle of Man TT community, we send our best wishes to Nicky Hayden and his family at this hard time", says the Official Isle of Man TT YouTube channel, which uploaded the video on Friday.
The 35-year-old American was hit by a vehicle while training south of the Italian seaside resort of Rimini on Wednesday and was rushed to hospital with severe chest and head injuries.
Hayden's fiancee Jackie and team members were joined at his bedside by brother Tommy and mother Rose who flew in from the United States.
"The young man, who is still in the intensive care unit of Cesana's Bufalini hospital, has suffered a serious polytrauma with subsequent serious cerebral damage", read a statement from the hospital.
Popular American World Superbike Championship rider Nicky Hayden is being treated for serious head and chest injuries following a road accident in Italy on Wednesday.
Honda said he was taken initially by ambulance to a hospital near the coastal resort of Rimini, before then being transferred to Cesena.
Valentino Rossi said: "It's a great shame because Nicky is a great rider for sure, a great talent, a world champion and always at the top, but especially a very good guy".
Hayden competed in the Italian round of the Superbike World Championship at Imola last weekend.
The 35-year-old Hayden won the MotoGP title in 2006. After the race we shook hands and hugged. He started 216 races between 2003 and 2015, winning three. "For Nicky, we're all with you", the Italian MotoGP legend added.
Michele Scarponi, the 2011 Giro d'Italia cycling champion, was killed last month after being hit by a van while training close to his home in Filottrano in eastern Italy.