Australia's five-times 500cc motorcycle world champion Michael Doohan believes that American Kenny Roberts Jr was a deserving winner of this year's title.

Roberts, the 27-year old son of triple GP500 champion Kenny Roberts, clinched the title by finishing sixth in Saturday's 500cc grand prix on the 4.9km Nelson Piquet Circuit in Rio de Janeiro, Brazil.

"Kenny has been scoring points more consistently than anyone else this year and that's what wins championships, so he deserves the title," said Doohan, "In Brazil he did what he had to do - it doesn't matter finishing sixth on days like this, because you just need to get enough points."

"When I won my first championship [in 1994] I felt good, but also relief because I'd finally done it, and I think Kenny would be the same."

After 14 of the 16 rounds, Roberts now has an unbeatable lead of 51 points over second-placed Rio race winner Valentino Rossi, with two races remaining at Motegi in Japan on October 15 and at Phillip Island in Australia two weeks later.

Doohan, who retired in 1999 because of injuries and is now Honda Racing Corporation's General Manager of Racing, said Roberts had benefited from being surrounded by his father and other American 500cc world champions Wayne Rainey and Eddie Lawson from an early age.

"When Kenny was young he used to train with his dad and guys like Rainey and Lawson, so he knew what it took to win a 500 championship," said Doohan, "I'm sure Kenny's family background with bikes has helped his career."

"Kenny's dad has put a lot into motorcycling, so it's good to see a family with so much tradition in our sport have some success."

Doohan said an unusual aspect of this year's championship to date was Suzuki had won three races, all by Roberts, compared to Honda's six victories and Yamaha's five.

"The Honda and Yamaha teams have more wins, but Suzuki and Kenny have the championship and that's what counts," he said.

Suzuki's championship ended six years of 500cc domination by Honda, with Doohan winning successive titles from 1994 to 1998, and Spaniard Alex Criville successful in 1999.