MULHEIM AN DER RUHR, Germany - Olympic medalists Zheng Siwei and Zhang Nan lost in the mixed doubles and men's doubles respectively here on Tuesday in the first round of the BWF World Tour German Open.

Along with his new partner Zhang Shuxian, Tokyo 2020 silver medalist Zheng Siwei was knocked out by German mixed doubles pair Jones Ralfy Jansen and Linda Efler 21-19, 21-17.

With his Olympic partner Huang Yaqiong, Zheng failed to make it to the second round of the World Championships last December in Huelva, Spain. He has been training with 22-year-old Zhang for one month before their debut in Mulheim.

"We were expecting some challenges before the game. This is our first show on the World Tour. We have not trained together for long, so there was not too much chemistry between us," said Zheng.

"We actually kept leading the first game for a while with the lead of four to six points, but we lost the points quickly when the German pair pressed on the front field. Definitely, it wasn't our best performance," added Zheng.

"Hopefully we can do better in the Swiss Open."

Olympic champion in both men's doubles and mixed doubles, Zhang Nan, who was reunited with his former world champion partner Liu Cheng for the first time since 2019, lost to Thai duo Supak Jomkoh and Kittinupong Kedern 21-19, 21-19. The Chinese veterans told Xinhua that they hadn't found the right tempo they used to share.

"We haven't played together for a long time and we need some time to get the feeling back. We're three years older than the last time we were paired," said Zhang. "We did not play well today and did not stay focused enough while leading in the first game."

Elsewhere in the men's doubles, Tokyo Olympic silver medalist Liu Yuchen, paired with new partner Ou Xuanyi, defeated Danish duo Rasmus Kjaer and Frederik Sogaard 21-15, 22-20.

World Championships winner Tan Qiang and his new partner Ren Xiangyu failed to advance to the next round by losing against Japanese pair Akira Koga and Taichi Saito 21-18, 12-21, 21-15.

Olympic champion Chen Yufei recovered from her ankle injury by smashing Phittayaporn Chaiwan of Thailand 21-13, 21-9 in the women's singles.

Zhang Yiman won against Spain's Beatriz Corrales in straight games 21-15, 21-14, while Wang Zhiyi was knocked out by eighth seed Ratchanok Intanon of Thailand 21-11, 21-18.

Liu Xuanxuan and Xia Yuting beat Danish pair Amalie Cecilie Kudsk and Signe Schulz 21-15, 21-12 in the women's doubles, and Lu Guangzu took an easy win over French shuttler Thomas Rouxel 21-13, 21-8 in the men's singles.