Alexander Zverev suffered another Grand Slam letdown with a five-set defeat by fellow young gun Chung Hyeon in the third round of the Australian Open.

The fourth seed is the highest-ranked player to fall so far in the men’s draw, but it was the manner of this loss that will be the most concerning for Zverev and his camp.

The 20-year-old German got into a row with the umpire about the light on Rod Laver Arena and won just five points in the final set to go down 5-7, 7-6 (7/3), 2-6, 6-3, 6-0.

Zverev won five ATP Tour titles last season, including two at Masters level, and climbed to a high of third in the world, yet he has reached the fourth round at a slam only once and has not beaten a top-50 player over a best-of-five sets match.

Zverev has long been seen as the leader of the new generation and chose not to play at November’s inaugural Next Gen Finals because he had qualified for the elite ATP Finals the following week.

In his absence, it was Chung who triumphed and the 21-year-old Korean celebrated reaching the last 16 at a slam for the first time, where he will face either Novak Djokovic or Albert Ramos-Vinolas.

However, it was Zverev's heated conversation with the chair umpire that has raised eyebrows from the match.

Unhappy with the lighting in the arena, the youngster was adamant that he couldn't see the ball properly, refusing to play at one point.

This was until the umpire said he cannot do that, which led to fans booing the tennis star.

The full transcript can be read below.

ZVEREV: "It doesn't take that long to turn on a switch. What is this? For the last four games I've asked you to turn on the lights because it's dark."

UMPIRE: "I know."

ZVEREV: "Can we sit down and wait then because he's serving?"

UMPIRE: "We cannot wait then?"

ZVEREV: "Why?"

UMPIRE: "Because..."

ZVEREV: [Interrupts] "I can't see the ball, I can't see it. It's bordering on darkness I can't see it."

Not good at all for the youngster, and yet another Grand Slam where he's failed to show his true potential.