Here's why young gun Chung is enjoying the short clock

The shot clock allows bespectacled Chung  to clean his spectacles 

South Korea's Chung Hyeon said he hopes the shot clock being tested out at the inaugural Next Gen ATP Finals in Milan will become a regular feature on the Tour because it allows him to clean his spectacles without worrying.

The 21-year-old, who played in the tournament's first two-hour match on Thursday when he beat Italian qualifier Gianluigi Quinzi to win Group A, is easy to recognise by virtue of his white-framed glasses.

In hot conditions or long matches, however, he often has to wipe down his lenses - meaning he sometimes incurs the wrath of the chair umpire and receives a time warning.

Shot clock, one of several innovations being trialled in Milan, displayed on electronic boards in the corners of the court counts down 25 seconds, allowing Chung to get himself organised in time.

"I like shot clock, because sometimes I get a warning because I have to clean my glasses," said Chung, who has worn prescription sports glasses throughout his career and took up tennis to improve his eyesight.

"I get the warnings all the time in long matches. So I like the shot clock."

The world number 54 was pushed hard by Quinzi who he lost to in the 2013 Wimbledon junior final, winning 1-4, 4-1, 4-2, 3-4(6), 4-3(3) to claim his third straight round-robin victory.

All eight group matches before Chung's clash with Quinzi had been completed in less than two hours - averaging one hour 26 minutes as the ATP trials short sets and "no-ad" scoring.

In the semi-finals Chung will face the runner-up in Group B where Daniil Medvedev boosted his hopes of continuing with victory over American Jared Donaldson.

Medvedev won 3-4(3), 4-2, 4-1, 4-0 to send Donaldson home without a victory to his name. The Russian, one of three in the tournament for the world's top 21 and under, will make the semi-finals if Borna Coric beats Karen Khachanov later.