For Rafael Nadal, it's all about his troublesome left knee while for Novak Djokovic, the major goal will be to emerge from a minor slump.
Nick Kyrgios defeated three top-10 players on the way to the Acapulco title.
Nick Kyrgios out-lasted Wawrinka 7-5, 6-7 (3/7), 6-4 to book a meeting with John Isner for a place in the final.
Nick Kyrgios survived three match points to beat top-seeded Rafael Nadal 3-6, 7-6 (7/2), 7-6 (8/6) on Wednesday and reach the quarter-finals.
Roger Federer indicated in January that he would play at the French Open this year.
The incident happened during a match at the Kooyong Classic, where Bernard Tomic pulled a fast one on Nick Kyrgios.
The 31-year-old Scot had intended to play in Brisbane at the beginning of 2018 but was forced to withdraw with a hip injury.
After withdrawing from the Kremlin Cup, Nick Kyrgios said he was heading home to prepare for the 2019 campaign.
Australian Nick Kyrgios was on the end of a surprise first-round loss to the American qualifier Bradley Klahn, the world number 104 winning 4-6, 6-4, 6-3.
Team World slashed Europe's overall lead to 7-5 heading into Sunday's third and final day of the 2018 Laver Cup.
Swedish official Mohamed Lahyani triggered controversy last month after coming down from his chair to give advice to Nick Kyrgios at the US Open.
Roger Federer gave yet another sneak peek of his greatness with a spectacular shot that not only left the crowd dumbfounded but also got a priceless reaction from Nick Kyrgios.
Roger Federer will be seeking a 13th appearance in the US Open quarter-finals when he plays Australian John Millman.
Roger Federer made it 18 wins in 18 second round US Open appearances by seeing off error-plagued Frenchman Benoit Paire 7-5, 6-4, 6-4.
Australia's 17th-ranked Nick Kyrgios withdrew from the ATP Washington Open on Wednesday because of a hip injury.
Milos Raonic cranked up the fastest serve of the tournament on Wednesday with a 147mph (236.5km/h) howitzer.
Andy Murray gave an encouraging display in his first competitive match in 11 months after finally recovering from the hip problem that required surgery in January