roger-federer.jpg
Federer gets a challenge in his second-round match.  USATSI

In a shocking sweep, Stan Wawrinka was utterly dominated by American Tennys Sandgren 6-2, 6-1, 6-4 on Day 4 of the Australian Open. The 26-year-old Sandgren, the 97th-ranked player in the world, took advantage of a struggling Wawrinka, the 2014 Aussie champ, who has looked off since returning from a knee injury. In fact, Wawrinka didn't commit to the tournament until a day before it began, so he seemed fated for an early exit.

"I only had surgery five months ago," Wawrinka told the Associated Press. "To be that far already, it's more than what we could have expected."

Temperature was the theme of the day, as it reached 104 degrees Fahrenheit at the height of the afternoon. By the time Roger Federer played, it had dropped to "only" 84 degrees.

Federer hardly looked his best himself against Jan-Lennard Struff, but that didn't prevent the No. 2 player from a 6-4, 6-4, 7-6 (4) sweep. It was by no means a walk like his first-round victory, but it was a solid win for him nonetheless and kept him on his crash course to play Rafael Nadal, who hasn't broke a sweat yet in this Australian Open.

Novak Djokovic dropped his first set to Gael Monfils, but stormed back to win 4-6, 6-3, 6-1, 6-3. In spite of his early struggles, he continued his impressive comeback tour, as he looks to reclaim the championship at Melbourne. No. 7 David Goffin fell to Julien Benneteau in five tough sets 1-6, 7-6, 6-1, 7-6.

Djokovic said that he was having a hard time with the heat, as was Monfils. "It was obvious we both suffered on the court today," Djokovic said. "Really tough conditions -- brutal."

Looking ahead, Federer will be facing Richard Gasquet in the Round of 32 on Friday night. Djokovic will be taking on Albert Ramos-Vinolas, while Sandgren has unranked Maximillian Marterer. Marterer pulled out a tough win against Fernando Verdasco in a five-set romp, propelling him to the round of 32.

In the women's bracket, defending Wimbledon champion Garbine Muguruza fell to Hsieh Su-wei in two sets, 7-6, 6-4. Karolina Pliskova looked utterly dominant in a 6-1, 6-1 rout of Beatriz Haddad Maia.

No. 1 Simona Halep swept out Eugenie Bouchard 6-2, 6-2 as well, continuing to assert her dominance. No. 9 Johanna Konta was bounced by U.S. player Bernarda Pera in another upset. Also representing the United States, No. 17 Madison Keys crushed Ekaterina Alexandrova 6-0, 6-1 as well, and she will advance to the round of 32 to represent the U.S. women.

Angelique Kerber won on her birthday as well, sweeping Donna Vekic 6-4, 6-1. Afterwards, Margaret Court Arena sang happy birthday to the star, who was just grateful to win her 11th straight match. "Happy to be playing tennis again like 2016," said Kerber. She is now slated to face Maria Sharapova in the third round.

Halep will now face 24-year-old American Lauren Davis in the third round, while Pliskova will take on fellow country-woman Lucie Safarova. Keys is facing Ana Bogdan. There's no doubt all players hope the conditions will be a bit more favorable, but everyone that's played in Melbourne before knows how unforgiving it can be in January.