Roger Federer wins Australian Open in a dramatic fifth set that ended with a challenge

Issei Kato/Reuters

Roger Federer wins the 2017 Australian Open.

Roger Federer won his 18th career Grand Slam, beating longtime rival Rafael Nadal in an epic five-set match at the Australian Open, and enhancing Federer's case as the greatest men's tennis play of all time.

After Federer won the opening set 6-4, the pair traded three ho-hum sets to force a fifth and deciding set. It was the fourth time the pair went five sets in a Grand Slam final, the most in the Open era, according to ESPN.

The fifth set was a masterpiece.

In the fifth, Nadal quickly jumped out to a 2-0 lead, breaking Federer in the first game and then avoided several break points to hold his own serve in the second game.

But with Federer trailing 3-1, he finally broke through. Federer held his own serve to pull within 3-2. Then, after failing to convert on his first five break points of the set, Federer converted the sixth to level the fifth set at 3-3. Federer held on his serve again and then broke again on Nadal's next serve to win his fourth straight game and go up 5-3.

That set up the dramatic ninth game. Nadal jumped out to a 40-15 lead. Federer held off both break points with an ace followed by a cross-court forehand winner to send the game to deuce.

That's when things started to get a bit wonky.

On championship point, Federer initially had his first serve ruled out. He challenged the call, and replay overturned it, leading to a do-over.

The next serve was then ruled out and Federer challenged again. This time, Nadal didn't have a play on the serve, so if the call had been overturned, it would have ended the match. However, this time the review showed the call was correct and the match continued.

Nadal would hold on Federer's second serve and it was deuce again.

However, Federer forced his second championship point. After Nadal's weak return up the middle, Federer went for a forearm winner and the ball appeared to catch the line. But for the third time in the last three points, the call was challenged, this time by Nadal. 

The call was upheld and Federer was the champ.

Nadal's chance to win his 15th career Grand Slam, and pull within two of Federer, had been dashed. 

Issei Kato/Reuters

Rafael Nadal watches as Roger Federer kisses the Australian Open trophy.