LONDON -- China's reigning Olympic champion Chen Long ousted legendary teammate Lin Dan on Thursday to reach the men's singles quarterfinals at the All England Open Badminton Championships in Birmingham.

Lin, 36, is no longer the hot favorite at the All England Open where he clinched six titles. He edged Thai teenager Kunlavut Vitidsarn in three games in the first round but failed to match the world number 5 Chen as he lost 21-17, 21-8 in straight games on Thursday.

"Lin is always the best player, so I always treasure each time I play with him," Chen said.

In another second round matchup, world number 1 Chou Tien Chen from Chinese Taipei fought hard to edge his Japanese opponent Kanta Tsuneyama 19-21, 26-24, 21-13.

"I did not predict that I would play such a long game, especially during the second set," said Chou. "I am treating this as a warm-up before the Olympics and I hope I could get as many points as I can before going to Japan."

In the women's singles, defending champion Chen Yufei set up an encounter with Thai ace Ratchanok Intanon after beating another Thai player Busanan Ongbamrungphan 21-17, 21-13.

Olympic champion Carolina Marin from Spain defeated China's Wang Zhiyi in straight games. The eighth seed will face Japan's Akane Yamaguchi in the quarterfinals.