Once a race winner and title contender, Heinz-Harald Frentzen today drives a hearse and is recovering from knee surgery.

Driving a Jordan, the German was a standout of the 1999 season, winning races against the odds and remaining a championship dark horse until the final stages.

Now 47, the former Williams driver Frentzen has most recently been racing a Mercedes in Germany's GT Masters series.

But Kolner Express newspaper reports that he might be forced to sit out the 2015 season as he is recovering from a serious knee operation.

The publication said the long-term injury dates all the way back to 1999, when he crashed his Jordan at high speed in Canada.

"My knee is still swollen and tender and I have to be careful," said Frentzen. "It's my braking leg and in GT Masters you need to brake very hard."

While he recovers, it is reported that Frentzen has returned to his native Moenchengladbach to help with the running of the family business -- a funeral home.

"It's true," he confirmed. "Even in my formula one career from time to time I helped my father with the business and now I'm helping my sister Nadine-Nicole."

Their father, Harald, died in 2014.

Express said one of Frentzen's new roles is to drive the hearse -- a converted E-Class Mercedes.

Frentzen said: "I'm actually retired and at the moment I don't mind not racing in 2015. But one should never say never."