Alexander Zverev progresses into 10th Grand Slam semi-final after overcoming rising American star

Zverev was effusive in his praise for the 20-year-old's groundstroke ability.

He said: "Learner from the baseline was playing unbelievable.

"I don't think I've played anyone who plays that well from the baseline for a very long time.

"I don’t know what Michael Chang has done with him in the off-season, but it’s incredible.

"Without my 20 something aces, I probably would not have won today."

Scorching conditions outside Rod Laver Arena saw temperatures climb into the mid-40Cs.

Officials were forced to close the roof after the tournament's heat-stress scale reached its threshold of five just before the match began.

The entire contest was therefore played indoors, with air conditioning provided for spectators and competitors.

Tien had been aiming to become the youngest Melbourne semi-finalist in 34 years.

He demonstrated remarkable court craft throughout despite lacking his opponent's raw power and formidable serve.

The young American, guided by former French Open champion Chang, displayed exceptional touch on drop shots and impressive net skills that repeatedly troubled Zverev.

Despite trailing 5-3 in the second set tie-break, Tien produced what were arguably his finest moments of the match.

He hammered back an overhead past Zverev before unleashing a stunning angled forehand winner to claim the set.

However, the American's relative inexperience became apparent in the third set, where he struggled to maintain his earlier intensity.

The fourth set saw Zverev face a set point at 5-6, which he saved with a powerful serve before taking complete control of the subsequent tie-break.

The 28-year-old now stands one victory away from reaching his third grand slam final.

The German is set to play in the semi-final match on January 30.

He will be hoping to add to his 24 career singles titles.

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