Novak Djokovic—the No. 1 player on the ATP World Tour—was surprisingly defeated by Bulgarian Grigor Dimitrov in the second round of the 2013 Madrid Open, leaving the door wide open for another top contender to win the tournament.
It's a rare thing to see Djokovic lose so early in a tournament, but the road to glory is now a bit less of a challenge for the rest of the field.
That said, speaking of the rest of the field, it's loaded.
Djokovic wasn't the only top male tennis player to enter, and there will be some serious competition from now until the final.
Here are the top men's tennis players left in the field.
Rafael Nadal (ATP World Tour No. 5)
The master of clay himself, Nadal, has been on fire since returning to the ATP Tour in February after a seven-month hiatus while recovering from knee injuries.
Can anyone beat Rafa on clay right now?
He's won four of his six tournaments since the return, and now that his legs are fresh, he looks ready to make a strong run at the three Grand Slams left on the schedule, beginning with his favorite venue—the French Open.
Nadal's first test at the Madrid Open comes on Wednesday, when he'll face Benoit Paire in the second round. Although every pro tennis player is a challenge, Paire (No. 37 in the world) shouldn't test Nadal too much.
It would be even more of a shock to see the Spaniard clay master lose on Wednesday than it was to see Djokovic lose on Tuesday.
Roger Federer (ATP World Tour No. 2)
In preparation for the French Open, Federer looked good in his first match against doubles specialist Radek Stepanek, who is trying to work his way back into the swing of things after neck surgery sidelined him in January.
While nobody truly expected Stepanek to defeat Federer, it was good to see him play well after his two-month layoff.
Federer needed the break. His back was clearly bothering him during the tournament at Indian Wells, and if he's going to continue to be a factor in Grand Slam tournaments going forward, he needs to take a different approach than he has done throughout his career.
He spoke about the break to reporters back in March, via BBC.co.uk:
I can't play a year like I did last year every single season. That isn't the point I'm at in my career. I'm not 22 where I have to play 25-30 tournaments a year. Plus, I believe I'll be really ready for the tournaments I've entered.
With a rested body and clear mind, Federer should be a tough out for any man in the field—including Nadal.
Andy Murray (ATP World Tour No. 3)
Murray is a man to be reckoned with on the ATP these days.
He fell just short of winning the 2013 Australian Open, losing in four rounds to Djokovic, and has won two other tournaments already this year.
Murray defeated Germany's Florian Mayer 7-6 (13-11) 7-6 (7-3) in the second round in a brutal two-round affair that lasted over two hours. He labored physically during the match, and according to Jonathan Overend of BBC.co.uk was grabbing his lower back.
If Murray can avoid getting tangled up in such arduous matches going forward, however, he has the skill to make a run at Federer and Nadal.
Follow me on Twitter @JesseReed78