Aprilia MotoGP team boss Fausto Gresini's condition was on Thursday described as "critical" by doctors treating the former Italian motorcycling world champion for coronavirus.
Gresini, 60, remains in a medically-induced coma in the intensive care unit of Bologna's Maggiore Hospital where he was admitted after Christmas.
"Unfortunately complications have occurred which have made the current clinical picture critical," Dr Nicola Cilloni said in a statement.
"Gresini is still hospitalised due to a persisting severe respiratory insufficiency following a Covid-19 infection.
"He is supported by a mechanical respirator and in a medically-induced coma.
"The hospital staff are continuing the treatment with the highest-possible intensity with a hope of the recovery of the organ functionality which has been severely compromised."
Gresini was hospitalised on December 27 in his hometown of Imola and was later transferred to hospital in Bologna.
The manager of the Aprilia Racing Team Gresini MotoGP team, he won two world championship titles as a rider in the 125cc class in 1985 and 1987.
But his team has had a tragic recent history with Japan's former 250cc world champion Daijiro Kato dying after a crash during the 2003 Japanese Grand Prix.
Tragedy again struck in October 2011 when Italian rider Marco Simoncelli died after an accident at the Malaysian Grand Prix.