Nick Kyrgios crashed out of the Shanghai Masters in the first-round after a three-set defeat against world No 104 Bradley Klahn.
The Australian, who has fallen to world No 38 - his lowest ranking since February 2016, was accused of 'borderline' tanking by chair umpire Damien Dumusois during a 4-6 6-4 6-3 to the American qualifier as he suffered further disappointment in the Masters 1000 tournament.
Kyrgios sensationally quit his opener at the event last year and was suspended for eight ATP tournament weeks for his behaviour at the 2016 edition.
The 23-year-old started encouragingly as he secured the first set but Klahn, in his tournament debut, responded impressively as one break in the final two sets proved enough to secure a surprise victory .
Kyrgios appeared disillusioned towards the latter stages of the match, before leaving the court using his phone, as Klahn, who began the year outside the world's top 200, made only seven unforced errors in the match.
Klahn will next meet 13th seed Borna Coric, who secured his first victory over three-time Grand Slam champion Stan Wawrinka in four meetings with a comeback 4-6 6-4 6-3 win against the former world No 3.
Meanwhile Milos Raonic also suffered an early exit as the 2016 Wimbledon finalist lost against qualifier Mackenzie McDonald.
The former world No 3, without a title since 2016 after a series of injuries, had defeated the American at Wimbledon this year but was beaten 6-3 5-7 6-3 in the Masters 1000 opener.
Raonic fired 23 aces against the world No 78 in China but the sixth seed, whose serve was broken three times, was unable to build on last week's run to the Japan Open quarter-finals.
Stefanos Tsitsipas, whose own run to the last eight in Tokyo last week was good enough to book his spot at the NextGen ATP Finals in November, opened with a hard-fought three-set win against Gael Monfils.
The Greek 20-year-old, seeded 10th, needed two hours and 33 minutes to overcome the experienced Frenchman 7-6 (7-4) 4-6 6-4 and book a meeting with Karen Khachanov.
Sam Querrey hit 14 aces as the American defeated world No 16 Diego Schwartzman 6-3 6-4 in 67 minutes and set up a second round meeting against countryman Taylor Fritz, who beat Robin Haase 6-3 7-6 (7-3).
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