As this year's Australian open reaches the final stages, the big names of tennis are coming into their own, with stars such as number one seed Novak Djokovic going up against Japan's Kei Nishikori today, as they both compete for a spot in the semi-finals.
World number two Rafa Nadal and Greece's Stefanos Tsitsipas have already booked their place in the semi's and will play each other tomorrow.
Moving over to the women's singles and there has been somewhat of a giant-slaying as 23-time Grand Slam winner Serena Williams was knocked out of the tournament in the quarter-finals after she lost to the 26-year old Czech Karolina Pliskova, despite having a 5-1 lead in the third set.
With the score at 40-30 on serve and match point, Serena's place in the semi-finals looked all but a formality.
However, an unusual foot fault seemed to unsettle the American and then the following point ultimately changed the outcome of the match.
As you can see below, Williams appeared to roll her ankle while changing direction and after hitting a forehand into the net, immediately held her foot in pain.
Nevertheless, Williams shrugged it off and continued playing, and despite clearly not moving quite as freely as before, she judged it not to be serious enough to call her trainer out to have a look.
Pliskova saw a chance to capitalise and did just that as 37-year old Williams failed to convert any of her four match point opportunities in a set the Czech star went on to win 7-5.
Despite her unfortunate injury, Williams hasn't blamed it for her defeat to Pliskova, instead admitting she was simply out-played.
"She was hitting lines and went crazy. She played unbelievable on match points," Williams said.
"It was nothing to do with my ankle. Obviously I made some mistakes but she played really well.
“There’s nothing I did wrong on those match points. I can’t say that I choked. She literally played her best tennis ever on those shots.
“I don’t really take losses well. But Karolina played lights out starting 5-1, 40-30. Literally, I’ve never seen anything like it. If anything, I think that’s a little bit easier to know, OK, next time I’m up 5-1 against anybody, I just need to make sure I play lights out when I have match points."
Tomorrow's two semi-finals will see Danielle Rose Collins from the US go up against another Czech tennis star Petra Kvitkova.
Meanwhile, Pliskova will meet Japan's Naomi Osaka, who Serena Williams lost to in last year's US Open final.