Honda driver Tiago Monteiro has been forced to withdraw from a second successive round of the World Touring Car Championship in Japan this weekend on medical grounds.
The Portuguese driver has since undergone further medical examinations, and has been advised to miss the forthcoming event at Motegi.
"This is one of the most disappointing moments of my career," said Monteiro.
"As a team, we've worked so hard to get ourselves into a championship-winning position, and to see it slipping away like this is very tough to deal with.
"The most frustrating thing is that the recovery is actually going very well; it's just that time is against me, but all of these things are motivating me to come back even stronger when the time is right.
"I have to thank the incredible medical team that are working with me every day - we share a common goal to return to racing as soon as possible - and everybody who has sent me kind messages of support through this difficult time."
Honda said it would announce a replacement in due course.
Gabriele Tarquini stood in for Monteiro in China, but has been precluded from doing so again in Japan due to clashing commitments with Hyundai's TCR programme.
Monteiro had led the championship prior to his withdrawal from the Ningbo event, but currently trails Volvo driver Thed Bjork by half a point in the drivers' standings.