Nicky Hayden's medical condition was called "extremely critical" by the hospital in Italy where he was taken after he was hit by a vehicle while bicycle training Wednesday.
The 35-year-old's fiancee and team members were at his bedside, according to the statement.
UPDATE: Nicky has now been joined by his brother Tommy and mother Rose who arrived in Italy from the United States earlier today.
"The clinical conditions of Nicky Hayden, hospitalized on Wednesday, May 17, remain extremely serious in the hospital resuscitation department of the Bufalini hospital in Cesena", a statement read.
"He is still in intensive care and suffered a severe polytrauma, resulting in very serious brain damage", the hospital added. He was rushed to the hospital, and a recent update from his team confirms he is in "extremely critical" condition. The Superbike World Championship says the incident occurred along the Rimini coast, Italy, Wednesday. He spent a further nine years in MotoGP racing with Ducati and the Aspar team before making a switch to the Superbike series and now rides for the Red Bull Honda World Suberbike Team. Hayden, who was in Italy following a race at nearby Imola, was transported to a local hospital for treatment.
He won the MotoGP championship in 2006 and has been competing for Team Honda in the Superbike category since a year ago.
"Nicky is one of the best friends I've ever had in the paddock", wrote the seven-time MotoGP champion on Instagram.
Hayden, nicknamed the "Kentucky Kid", won the 2006 MotoGP world title before moving to the Superbike World Championship for the 2016 season. After the race we shook hands and hugged. In the MotoGP, he ran 218 Grand Prix races with three wins and 28 podium places. He further said "Come on Nicky, we're all with you".
Britain's Tour de France champion Chris Froome escaped unhurt this month while having his bike written off in a hit-and-run incident near his Monaco home.