Novak Djokovic beat Gael Monfils in four sets to advance from the second round of the 2018 Australian Open on Thursday, but 2014 champion and ninth seed Stan Wawrinka was dumped out by Tennys Sandgren in straight sets.
There were also upsets in the women's draw as third seed Garbine Muguruza was beaten by Hsieh Su-wei and ninth seed Johanna Konta lost to world No. 123 Bernarda Pera.
However, Maria Sharapova, Angelique Kerber, Madison Keys and Simona Halep all made it through their second-round matches on Thursday.
Here are the details for where to catch highlights of the action from Day 4 in Melbourne:
TV Info: Eurosport 1 (UK) and ESPN2 (U.S.)
Live Stream: Eurosport Player (UK), Tennis Channel Everywhere (U.S.), WatchESPN (U.S.)
Wednesday Replay: Eurosport 1 from 1:30 p.m. (GMT), Tennis Channel from 12 p.m. (ET)
Full Results and Schedule: AusOpen.com
Djokovic is a six-time winner at the Australian Open, and he reached the third round of the tournament for the first time since 2016 as he downed Monfils 4-6, 6-3, 6-1, 6-3 in searing heat on Thursday.
The Frenchman made the ideal start as he went a set ahead in his bid to oust the former world No. 1, but the soaring temperatures then seemed to hamper Monfils, per Live Tennis:
Djokovic took advantage as he levelled the match before taking the third set in double-quick time by breaking Monfils three times.
Despite a rally from the Frenchman he was unable to take any of the five break points he earned in the fourth, while Djokovic took the single break point he needed to see out the match.
Wimbledon champion Muguruza was another who struggled in the heat as she was downed by Taiwanese player Hsieh, who won their contest 7-6 (1), 6-4.
The highest seed to fall in either the men's or women's singles, the Spaniard made almost 40 unforced errors in the match and paid the price.
There was no such trouble for top seed Halep, who beat Eugenie Bouchard 6-2, 6-2 in just over an hour, or American Keys as she downed Ekaterina Alexandrova 6-0, 6-1 in 41 minutes, per tennis commentator David Law:
Three-time Grand Slam champion Wawrinka was far from his best on Thursday as he was knocked out by America's Sandgren.
It was arguably the shock of the men's draw so far but looked inevitable with the world No. 97 cruising at 6-2, 5-0 ahead.
Wawrinka showed some fight in the third set but did not break once in the whole match, and Sandgren's consistency proved too much in the end.