Hyeon Chung became the youngest man to reach the semi-finals of a Grand Slam for eight years as he defeated fellow surprise package Tennys Sandgren in straight sets at the Australian Open on Wednesday.
This has been one of the most unpredictable men's tournaments for many years and Chung joins Kyle Edmund in making it through to the last four as an unseeded player as he converted on his sixth match point for a 6-4, 7-6 (7-5), 6-2 victory.
Yet, what was so remarkable was one rally in particular, when both players were playing so casually, and they were hitting back and forth simple backhanded slice shots.
The crowd became very amused as the rally lasted for 31 shots with both players hardly breaking a sweat.
At world No 58, he is also the lowest-ranked man into the semi-finals at Melbourne Park since Marat Safin in 2004, but he went into the match as the favourite against 97th-ranked Sandgren, whose run to the last eight has been remarkable.
The 21-year-old, the youngest man to reach this stage since Marin Cilic here in 2010, was only really troubled in the second set, when he had to fight back from 5-3 down.
Sandgren kept his hopes alive by saving four match points, one of them with incredible reflexes at the net, but Chung took his fifth chance and will play either Roger Federer or Tomas Berdych.
You can watch the rather bizarre rally in the video below.
"In the last game, 40-0 up, I was starting to think what I had to do afterwards but after the deuce, break point, I just keep focused," he said.
Asked who he would prefer to play, a smiling Chung said: "I don't know. 50-50, whoever wins, I'm playing, I don't care."
Chung had beaten fourth seed Alexander Zverev and six-time champion Novak Djokovic en route to the last eight, and found himself the favourite in his first Grand Slam quarter-final.