The 2019 Australian Open has already produced two major upsets: Earlier this week, Swiss superstar Roger Federer fell to Greek upstart Stefanos Tsitsipas in an ugly loss during the tournament's 4th round. (Tsitsipas himself then fell in the semi-round to Rafael Nadal).
In an arguably more shocking turn of events, Serena Williams's epic collapse against 7th seed Karolina Pliskova stunned the Open, and denied Williams a rematch against Naomi Osaka, who shocked the world last fall by beating the tennis great at the U.S. Open last year, and winning this year's Australian Open.
Upsets, however, are what make a Slam tournament interesting. In this Golden Age, upsets have been few and far between in men's tennis, which only makes them even more shocking. While the women's game has been more inconsistent, there has been one constant, and that's Williams. More than any other champion, her losses seem stunning and unexpected.
With that in mind, CNBC recently took a look at other instances in the last decade where a Grand Slam tournament resulted in a shocking upset, in no particular order.
Robin Soderling over Rafael Nadal, 2009 French Open
Nadal entered the contest as a 4-time defending champion that had obliterated the 25th ranked Swede on red clay just two weeks prior, in Rome. Coming into the match the King of Clay hadn't lost a set all tournament. But Soderling's shock victory was short lived: He fell to Roger Federer in the final, who himself had lost to Nadal in 3 consecutive years.
Just as he was peaking in the rankings in early 2011, Soderling's career was cut short by a variety of ailments.
Roberta Vinci over Serena Williams, 2015 US Open
Williams was two matches away from the ultimate achievement: a calendar year Grand Slam. And there seemed to be little to be concerned with before her match against Vinci, since Serena had never dropped a set in their four prior encounters. But the diminutive Italian, in her first ever Slam semifinal at the age of 32, played a strategically brilliant last two sets, absorbing Serena's pace and disrupting Serena's rhythm, and pulled off the epic upset.
Vinci would lose in the championship match to surprise finalist Flavia Pennetta. Though she was never able to win a Slam title in singles, Vinci did retire in 2017 with five doubles Slam titles.
Nick Kyrgios over Nadal, 2014 Wimbledon
Nadal was the world number one and came into Wimbledon on the heels of his 9th French Open victory, hoping to add a third Wimbledon title to his collection. Kyrgios was only 19, and had to be granted a wild card entry into the draw.
Kyrgios took full advantage of the opportunity. Wielding his explosive service game and employing a hurried style of play that discomfited Nadal, Kyrgios — a talented but short-tempered and inconsistent player — was able to claim the biggest victory of his career.
Sergiy Stakhovsky over Roger Federer, 2013 Wimbledon
As the defending Wimbledon champion, Federer seemed to be in form at the start of the tournament. But after winning the first set against an inspired 116th ranked Stakhovksy, Federer started spraying a slew of unforced error, while Stakhovsky played his outdated serve-and-volley game to absolute perfection. The now 33 year-old Ukrainian is still on the pro tour but he has never advanced farther than the third round of a major.
Sabine Lisicki over Serena Williams, 2013 Wimbledon
Williams had just taken home the title at her "least successful" Slam at the French Open. A rash of upsets had spread through the tournament so by the time of this encounter Serena was an even more prohibitive favorite to take the title.
However, the German outplayed Williams in the first set, blowing winners and serving a multitude of aces past the stunned American. Since that time, Lisicki hasn't been able to be much of a factor in the Slams, and has battled injury problems.
Steve Darcis over Nadal, 2013 Wimbledon
Though he had won his 8th French Open weeks prior, Nadal pulled out of a grass court warm up due to fatigue. Even so, a loss to the 131st ranked player in the world was no less shocking. Darcis played the match of his life in defeating a sub par Nadal, who did recover to win the US Open two months later. As for the 35 year-old Darcis, he's still on tour, ranked 321st.
Sam Querrey over Novak Djokovic, 2016 Wimbledon
Two weeks before Wimbledon commenced in 2016, Novak Djokovic fulfilled his lifelong dream of hoisting the French Open trophy, and entered Wimbledon as a prohibitive favorite. Yet Querrey played a brilliant match, finally capturing a big victory and sustaining enough momentum to push into the semifinals the next year.
John Millman over Roger Federer, 2018 U.S. Open
Yes, Federer was 37 at the time, but his loss to a 28-year old journeyman was still a shock. Millman played an aggressive match, taking frequent chances on his ground strokes and pummeled Federer all night.
The glory didn't last long though, as Millman bowed out in the next round against Djokovic. The win did propel him to a career high of 38 though, and he reached the second round of this year's Australian Open.
Naomi Osaka over Serena, 2018 U.S. Open
Returning to competition form after giving birth, Williams looked in peak shape – but ultimately fell to Naomi Osaka in a dramatic finish marred by a controversial penalty against Williams. Still, a number of observers noted that Osaka had thoroughly outplayed Williams, who's still chasing her elusive 24th Slam title.
Clarification: Swiss superstar Roger Federer fell to Greek upstart Stefanos Tsitsipas during the tournament's 4th round.