Fernando Alonso's place on the grid at the Chinese Grand Prix is yet to be confirmed, with the McLaren driver still waiting on medical clearance.
The two-time world champion was involved in a heavy crash at Formula One's season-opener in Australia, and was forced to miss the Bahrain Grand Prix after suffering lung and rib injuries.
Alonso is continuing his preparation as normal, but concedes he cannot be sure of being involved in Shanghai this weekend.
"It was disappointing to be told I couldn't race in Bahrain, but I fully respected the decision of the FIA medical team," he said.
"While I hope I'll be back in the cockpit on Friday, until I get the all-clear from the doctors to race - whenever that may be - we cannot assume anything, but I'm continuing to prepare for the race weekend as normal."
Reserve driver Stoffel Vandoorne took Alonso's place in Bahrain, securing a point on his debut with a 10th-placed finish.
"Stoffel did a great job in Bahrain, and although Jenson [Button] suffered reliability issues, it was positive to see that both cars ran quite strongly during the weekend," Alonso added.
McLaren racing director Eric Boullier added: "Once again, Stoffel will be on standby until Fernando has his routine meeting with FIA doctors on Thursday, and until then we will be readying ourselves as normal."
"Fernando has been recuperating at home and training as usual, and we, like him, hope to see him back in the car. We'll accept the outcome - whatever that may be - and plan accordingly."