Lin Dan ran over Lee Hyun-il of South Korea 21-12, 21-10, and No. 2-ranked Chong Wei beat No. 3 Chen Long of China 21-13, 21-14, securing for Malaysia a fifth ever Olympic medal, all of them in badminton.
Chong Wei won the fourth medal, a silver, in Beijing, where he was routed in the final by Lin.
But Lin and Chong Wei have remained the two biggest stars in the game, and their world championships final in the same Wembley Arena nearly a year ago was an instant epic that fans hope will be repeated on Sunday.
"I'm really happy that I get to meet my old opponent as we are the same age and we get to play at the final of the Olympics," Lin said.
"It's really good as it shows that we have not been knocked out by time.
"I hope we can get to our potential and achieve our medal dreams and I want to wish Lee luck in that, too."
Their clash will salve badminton after four women's doubles teams were disqualified for trying to lose group matches to rig favourable quarterfinal matchups.
The women's final on Saturday will be an all-Chinese contest between world champion Wang Yihan and the only players she fears, Li Xuerui.
China won the first gold of an attempted sweep of all five events when world champions Zhang Nan and Zhao Yunlei won the mixed doubles final. Zhao could add the women's doubles gold on Saturday.
Lin and Lee Hyun-il have been playing each other for a decade, and their matches this year in the Korea Open and Thomas Cup were tough. But Lin earned his best win over Lee in four years as he raced 11-1 up. The Korean admitted he was overwhelmed and tired from the day before, when he got revenge on Lin's Chinese teammate Chen Jin, who beat Lee in the Beijing bronze-medal playoff.
Lee will play for bronze again, against Chen Long.
Chen had won three of his five matches with Chong Wei since September, but Chong Wei imposed his will early. He didn't let rallies develop, attacked quickly, and frequently caught Chen flat-footed and bemused.
Chong Wei showed off his command midway through the second game when he tracked Chen's clear to the baseline. He checked the lines as the shuttle fell and it looked as if he was going to let it drop. But he suddenly whipped it back off his hips, saved a smash from Chen, then watched Chen put a soft backhand into the net.
Another netted backhand by Chen gave the match to Chong Wei, who dropped to his knees, pumped his fists, kissed the court, stood up and pumped his right fist twice more.
"I didn't expect to win because my preparation has only been 50 per cent," Lee said. "But when it was 11-4 I played more confidently. I worked hard until I could kill the shuttle."
Ten weeks ago he didn't think he'd make the Olympics when he tore ankle ligaments and was carried off in a wheelchair at the Thomas Cup in China. But daily treatment of 13 hours and a resolve like no other has got him playing for Olympic gold again.
In women's action, Wang Yihan thumped Saina Nehwal of India 21-13, 21-13. Then Wembley Arena became subdued as the crowd had no underdog to inspire in the second semifinal, where Li edged Chinese teammate Wang Xin 22-20, 21-18.
Wang Yihan had a distinct advantage in height and reach on Nehwal but she won't against Li, who can almost match her at eye level. Li can certainly match her on court.
Li burst into Olympic contention only this year, and suddenly turned into a gold-medal tip as she won 30 successive matches from February to June, including wins over Wang in the All England Open final, Asian championships final and Indonesia Open semifinals. Wang has topped the rankings for at least 18 months, but not played like the No. 1 this year.
Still, being 13 centimetres (nearly halfa foot) taller and quicker was good enough for Wang to blunt Nehwal's grit and tactical nous. Nehwal, whose confidence was high having beaten Wang Xin and Li Xuerui in her 14-match winning streak, did her best to move Wang Yihan to the corners and drop shot her, but Wang's speed didn't leave the court open for long.
Afterwards, Wang hugged her coach, the Olympics' only two-time women's champion Zhang Ning, whom she can follow into history on Saturday.
"I would be happy to get the gold medal but for the Chinese team to get all three medals it would be the best," Wang said.
Zhang gave no instructions to Li and Wang Xin other than to play their best. Li had never beaten Wang Xin but this was their first match since November, and Li was no longer an easy-beat for Wang.
Winning the first game was the turning point. In the second game, Li got ahead early and had the confidence to stay in front. When she won, her scream was her first real sign of emotion, and let Wang Yihan know who's coming.
"I have a must-win attitude," Li said. "I'm very excited about tomorrow's match and I am very much inspired."