Farewell race: 'Not at his best' but gold-chasing Bolt has plans in place

'I think it will have to be 9.8 low, perhaps the same time it took me to win at the (Rio) Olympics'

Jamaica's eight-time Olympic gold medallist Usain Bolt says he thinks he will need to produce a time similar to the one that earned him gold at the Rio 2016 Games to win Saturday's 100m final at the World Athletics Championships in London.

The 30-year-old is competing in his seventh and final World Championships, and recently clocked a season's-best time of 9.95 seconds in a Diamond League meeting in Monaco.

He told Reuters he is "not at my best but where I want to be" and has predicted he will have to set a new season's best to win and add another gold medal to his collection at the London Stadium -- where he won Olympic gold in 2012.

"I think it will have to be 9.8 low, perhaps the same time it took me to win at the (Rio) Olympics, I think it will take the same time to win here or close to that," said Bolt, who clocked 9.81 seconds to clinch gold in Rio.

"I'm feeling good, I'm feeling better after every race. Everything is going good."

One of Bolt's biggest rivals for gold in London was expected to be Canada's Andre de Grasse, but a Grade 2 hamstring tear in his final training session has ruled de Grasse out of competing.

De Grasse said the prospect of missing out on what he called "the focus of my season" was "unimaginable", but Bolt said it was vital for his future career prospects that de Grasse took a realistic approach to his injury.

"It's always about listening to your coach and taking the doctor's advice and taking your time to recuperate while working as hard as possible to get over the injury," said Bolt.

"Sometimes when you rush it only makes things worse. I hope that he takes heed, takes his time to heal and hopefully everything goes smoothly so that he can get back on track next season.