Few even knew how to pronounce his name right.

Now everyone knows his game, as well as his proud identity as the finest representing China's ethnic groups in men's professional tennis.

Buyunchaokete, a 22-year-old tennis player hailing from the Mongolian ethnic group in Northwest China, delivered a bittersweet upset for the Beijing crowd on Friday after he came from one set down to outlast higher-ranked compatriot Shang Juncheng, a native of the Chinese capital, 6-7 (3), 6-2, 6-4 on Friday to advance into the second round for the first time in his career at the China Open.

It was the first all-Chinese main-draw clash ever at the ATP 500 tournament, which drew a small but enthusiastic crowd at Beijing's National Tennis Center during a workday morning session to cheer for both players, with Shang the apparent favorite.

It was Buyunchaokete, though, who overcame the high-stakes pressure and stepped up a gear in the second and third sets to deny the 19-year-old Shang another deep run following the teen star's triumph at last week's ATP 250 event in Chengdu.

Buyunchaokete, or simply known as Bu by his increasing number of fans, will next face Italy's No 6 seed Lorenzo Musetti, who beat Belgian qualifier Zizou Bergs 7-5, 4-6, 6-3 on Friday, in the second round.

The loss has snapped Shang's five-match winning streak, which carried him all the way to win his maiden career Tour-level title in Chengdu on Sunday to become the first Chinese man to win a home tournament on the ATP Tour.

"I've really started to enjoy tennis, after having finally fought into the top-100," said Bu, who cracked the world's top-100 for the first time last week after making his first Tour-level semifinals at another Chinese tournament in Hangzhou.

"Now I have to set higher goals for myself and keep working harder," he said.

The flying start in Beijing has lifted Bu to No 89 on the live ATP rankings, with Shang ranked at 51st as the second-highest ranked Chinese man led by top ace Zhang Zhizhen at No 41.

Shang congratulated Bu's breakthrough win at the ATP 500 level, attributing his loss to the lack of consistency in his own form.

"I am really excited to be able to play at the Diamond Court where I started watching tennis and grew interested in the sport," said Shang, who was brought to the tournament for the first time by his parents at the tender age of five.

"Bu played really well today with a strong serve and aggressive game that he carried over from Hangzhou last week. I had expected his level because I believe he belongs to the top-100, but I didn't perform to my best today."