Never the tallest, or the biggest among his peers when growing up, China's tennis prodigy Shang Juncheng knows he has to pattern his game to be the fastest and sharpest.

And it has been working a treat for the 19-year-old southpaw, with many of "the youngest" records in Chinese tennis falling under his name. However, a reality check hit on Saturday to remind him how far he still needs to go.

As soon as the opening serve in his second-round match against Carlos Alcaraz at the Rolex Shanghai Masters, Shang realized he was hitting against the ultimate version of his type — a fast and furious attacker and an almost invincible defender, combined in one — after the Spanish four-time major winner broke him in the first game, setting the tone for a 76-minute straight-sets win.

Despite an early exit from his home ATP1000 tournament, the Chinese teen wrapped it up with nothing but positive takeaways after measuring himself against perhaps the highest benchmark of his archetype.

"Somehow, in someway, I feel like we are playing a similar style of tennis. For sure, he is a lot more powerful and more aggressive than I am at the moment," Shang said after losing 6-2, 6-2 to Alcaraz, who is two years his senior, on Shanghai's central court in a rematch of their third-round clash at the Australian Open.

In their only previous meeting in January, Shang had to retire due to a right thigh injury with Alcaraz leading 6-1, 6-1,1-0 in a round-of-32 match at Melbourne Park.

Standing 1.8 meters tall, while weighing 73 kilograms, Shang seems close in size with Alcaraz, but saw his quick-firing game, which would be dangerous against many others, outpaced by the Spaniard's next-level intensity and consistency.

"I need to build my power, which is important facing an opponent like him, and pick up my speed as well," said Shang, who in May became the youngest Chinese man to crack the top-100, and on Sept 24, the first to win an ATP Tour title on home soil at the Chengdu Open.

"I guess I'll never become the powerful type of player on the tour, or one of the biggest-serving players. I have to play the smart and agile way.

"It won't happen overnight, though. I just need to take it step by step and evolve my game. I feel like I am developing in the right direction."

A second-round appearance at his second home Masters campaign has seen Shang climb to No 49 on the live ATP rankings as of Sunday, only three places lower than the country's top ace Zhang Zhizhen, who was eliminated in the first round by Belgian Zizou Bergs.

The ascent of his young challenger has left Alcaraz intrigued, and on guard.

"We're going to share the court more and more often, for sure," said Alcaraz, who won his fourth title of the season at the ATP500 China Open in Beijing last week.

"We're going to play more important matches in the future, because he's going to be there, he's going to be at the top.

"I've seen his last couple of matches, he just got his first ATP title, which was impressive. I'm going to watch a lot of his matches and follow him, as well. I think he's going to improve fast and pretty well, so this is a guy who we have to keep an eye on and follow his results."

Having played just three matches on the North American hard-court swing across Cincinnati and New York, Alcaraz attributed his recent surging momentum in China to his freshness during the home stretch of the ATP season.

"I'm a guy that tries to see the positives. For example, on the American swing, it didn't go as I expected," said the No 3 seed, who suffered a shock US Open second-round defeat to Botic van de Zandschulp.

"So, I had more time to prepare for this part of the season. I had some weeks that I put in really good work, physically, in training, just to feel great coming to this tournament. I think that's the difference."