Not once, but twice — Buyunchaokete's recent back-to-back ATP semifinal runs have proved his huge potential as yet another emerging Chinese contender at the top of men's tennis.

Everyone close to him had predicted a bright future, yet a series of health issues bogged him down, leaving his promising career on the pro circuit on uncertain ground. However, Buyunchaokete proved his doubters wrong, big time, with two showstopping deep runs at home tournaments over the past two weeks.

The 22-year-old, hailing from China's Mongolian ethnic group, has fought his way from obscurity to stardom with two straight semifinal appearances on the ATP Tour, first in Hangzhou on Sept 23, and again in Beijing on Tuesday.

His surprising, second consecutive deep run — which was stopped by two-time major winner and world No 1 Jannik Sinner in Beijing — made Buyunchaokete, known as Bu to his growing legion of fans, the first Chinese man to enter the final-four at the ATP500 China Open, and the first to reach that stage at back-to-back ATP tournaments.

This year's Hangzhou Open was only his second ATP Tour event, following last year's wild-card entry at the Shanghai Masters. At the major level, he only managed to make his Grand Slam main-draw debut at the US Open in late August, after starting the season ranked as far back as 171st in the world.

From now on, though, it will be a whole new ball game for the ambitious and tenacious young man.

"I am quite tired today, feeling like I've run out of gas, and my serve was probably the worst (it has been this week)," Bu said of his brave 6-3, 7-6 (3) loss to Sinner in the semifinals on Tuesday — a match which coincided with China's National Day celebrations.

"Still, he only managed to break me once, and I put him under a lot of pressure on the baseline. I think I did a good job."

He sure did.

The daring underdog, cheered on enthusiastically by the partisan crowd at the packed Diamond Court, pushed the defending champion almost to the limit with a resilient game, especially in the second set, when Sinner had to step up an extra gear to outlast the home favorite in long rallies.

The Italian star, who is one year Bu's senior, joined the clapping crowd to acknowledge his opponent when Bu left the court to a standing ovation.

"I felt like he's an all-around, very good player. It's tough to play against him," Sinner said of Bu's game at the post-match news conference.

"He's a very solid player. He kept his level throughout the whole match, which is also sometimes tough to see... He doesn't really have any big weaknesses. Forehand, backhand, good serve, also the return game is very good. You have to earn every point you play. Physically he's good.

"Obviously, there are things he can, and will for sure, improve. He's making his breakthrough a little bit this year, the last couple of months, and hopefully he keeps going.

"He's obviously also very, very young. I have the feeling that we will see him more and more on the biggest stages."