Caterham driver Vitaly Petrov said Wednesday he is feeling unwell in the run-up to Sunday’s Japanese Grand Prix.

The Japan race could be crucial for Caterham, who are bidding to retake the tenth place in the constructors’ standings that they lost to Marussia in the last race in Singapore.

“I’ve arrived in Japan, don’t feel well somehow,” Petrov said on Twitter.

“I’ll get some treatment.”

Petrov is 21st in the championship after 14 of 20 races.

He has no world championship points this season and owed his place to a 13th place finish in Valencia in June.