China's Lin Dan celebrates beating India's Srikanth Kidambi on Wednesday. Wei Xiaohao / China Daily

Badminton world No 1 Lee Chong Wei still has the "anger" to prove himself a good player and an Olympic champion after a doping scandal that stained his record and set back his career, according to his coach Hendrawan.

The 33-year-old Malaysian is bidding for an elusive gold medal in his Olympic swan song in Rio after heartbreaking losses to Chinese great Lin Dan in the championship matches at the Beijing and London Games.

Lee will face Lin in the semi-finals, hoping desperately to topple his long-time nemesis and go on to end his nation's 52-year wait for a first Olympic title.

Although revered in Malaysia, two-time silver medalist Lee's halo slipped when he tested positive for dexamethasone, a widely administered anti-inflammatory used to treat asthma and altitude sickness, at the 2014 world championships.

He was provisionally suspended in November of that year and faced a career-ending ban, but the World Badminton Federation controversially handed him a retroactive eight-month suspension that allowed him to return to competition a few days after the judgment.

"He has had to move on from that. We are already past it. That was a story, but now we focus again," coach Hendrawan said this week.

"Only a year ago he was ranked No 180 in the world. He got back to No 1. That is also amazing, because Chong Wei still has anger to prove himself," added Hendrawan, an Indonesian.

"He feels determined to prove to himself that he is still a good player ... especially for the Olympics and the world championships."

The wiry Malaysian has been ranked world No 1 for much of the past decade, but has never won a major global title, frustrated repeatedly by 32-year-old Lin on the biggest stages.

He has lost to Chinese opponents in the finals of the 2011 and 2013 world championships and in the gold medal finals of the 2010 and 2014 Asian Games.

Lee has beaten Lin in their past two matches on the world tour, but the Olympics is a different stage as the Chinese pointed out after surviving a quarterfinal scare against India's Srikanth Kidambi on Wednesday.

Lee said that as world No 1 he is under pressure to win in Rio, but Hendrawan said he feels the Malaysian is coping better with it.

"He cannot run from that problem," said Hendrawan, a silver medalist at the 2000 Sydney Games.

"I have told Chong Wei he must try to accept this pressure."

Most badminton players in their thirties struggle to keep up with the fitness required in the modern game, but Lee and Lin have defied Father Time.

Lee hardly broke a sweat in a one-sided rout of Chinese Taipei's Chou Tien-chen in the quarterfinals on Wednesday, but his match against Lin is certain to be more taxing.

Hendrawan said Lin had altered his game a few years ago to try to conserve his energy, but Lee had taken longer to shelve his all-court style for a more aggressive approach aimed at killing points quicker.

"I have tried to make changes. Not change his game, but make it more complete," the coach said.

"He has plenty of power and speed, but we have been trying to make him more complete in his defense, make him more efficient in his rallies."