It seems Jordan Thompson's efforts in winning his first ATP Tour singles title and then the doubles crown in Los Cabos has caught up with him.
The 29-year-old spent more than 12 hours on court through his five singles matches, culminating in a memorable victory over Casper Ruud in the decider.
He followed up that success by combining with fellow Australian Max Purcell to triumph in the early hours of Sunday morning (AEDT), but it's played a part in both losing their first-round matches in Acapulco on Wednesday.
Thompson, now the world No.32, was beaten 6-3 5-7 6-4, in two hours 42 minutes, by Aleksandar Kovacevic, the 93rd-ranked American.
Compatriot Purcell was also bundled out at the first time of asking, going down 4-6 6-3 6-0 to eighth seed Frances Tiafoe.
Tiafoe will face German Dominik Koepfer, who took care of Frenchman Terence Atmane 6-4 4-6 6-0.
Daniel Altmaier pulled off a major upset by beating top seed Alexander Zverev in a battle of two more Germans.
The 27-year-old Altmaier and world's 57th ranked player defeated his countryman for the first time in three attempts and will play Serb Miomir Kecmanovic in round two.
Second seed Holger Rune eased past American qualifier Michael Mmoh 6-2 6-3 to advance.
The 20-year-old Dane reached the semi-finals in Acapulco last year and next plays Kovacevic.
Fifth seeded Stefanos Tsitsipas defeated Roman Safiullin of Russia 6-3 6-4 to move on to face Italy's Flavio Cobolli.
The 25-year-old Greek reached the semis last week in Los Cabos and is trying to win his first career 500 tournament.
"I knew that dealing with Roman, he's someone that can play good on these kinds of surfaces," Tsitsipas said in his interview on centre court.
"He takes the ball early, pushes you back. That was the main thing I had to deal with today, which I did pretty well."
Elsewhere, Norway's Casper Ruud outlasted Brit Christopher Eubanks 6-4 6-7 (5-7) 6-3 and is next up against Dusan Lajovic of Serbia, who beat local Rodrigo Pacheco 6-2 6-2.
With AP
