Valentino Rossi's forthcoming test in a 2008-spec Ferrari single seater is in doubt.
The reigning MotoGP champion was reportedly admitted to San Salvatore hospital in Pesaro, Italy on Thursday, with severe abdominal pain.
He was diagnosed with an inflamed appendix but not operated on, instead checking out of hospital with antibiotics.
Ferrari team boss Stefano Domenicali confirmed earlier this week that the 30-year-old is scheduled to test a F2008 for two days at Barcelona beginning next Wednesday.
The Italian is being linked with Ferrari's plans to enter a third car in the world championship, possibly with a small team.
"It's not sure that the third car will be allowed, but if it is, Valentino will be welcome," Felipe Massa said on Friday at the Madonna di Campiglio media event, according to Corriere dello Sport.
Domenicali added: "For us the third machine would represent a good move for F1, and especially if a driver like Valentino would be interested."