Alexander Zverev got extremely annoyed with Nacho Forcadell and it happened because of a very bizarre reason as the German couldn't believe that the chair umpire stopped a point because a feather fell onto the court.
With the world No. 2 up by a set but down 4-2 to Tommy Paul in the second set, a feather fell on his eyeline while he and the American were in mid-rally.
Since the game was at deuce and the 27-year-old felt he had a good chance to earn a break point, he lost it after the point was stopped and ordered to be replayed.
"This is unbelievable. It's a feather. There's millions of them on the court," Zverev told Forcadell.
After the incident, the second seed lost the game.
However, he was able to win the next three games - ultimately force a tie-break - and win it without a lost point.
In the end, the German completed a 7-6 (1) 7-6 (0) 2-6 6-1 win over Paul.
Zverev admits: Paul should have been up against me
Before blowing a 5-2 second-set lead, the American also failed to serve out for the first set while 6-5 up.
And after getting the job done in four sets, the two-time Grand Slam finalist was the first to admit that he probably should have been the one trailing and not the world No. 11.
"To be honest, I should have been down two sets to love. He played better than me. I was not playing great and I thought he was," Zverev reflected.
"I somehow won the first set, somehow won the second set, and I'm up two sets to love all of a sudden and I need only one more set.
"The fourth set was definitely the best that I've played and I'm obviously extremely happy to be back in the semi-finals now."
For a place in the Australian Open final, Zverev will battle against Novak Djokovic, who beat Carlos Alcaraz.
