Nick Kyrgios needed just 40 minutes on court to reach the second round of the Malaysian Open as Colombian opponent Santiago Giraldo retired with an illness, trailing 6-1 2-1.
The victory on Monday, highlighted by six aces off the racket of the seventh seed from Australia, was one of only two main draw matches played on opening day.
In the other, Australia took a loss when German Benjamin Becker beat Sam Groth 6-1 7-6 (7-5).
Kyrgios will now play either Tatsuma Ito or Finn Jarkko Nieminen in the second round.
Kyrgios is playing this week for the first time since losing in the US Open first round to Andy Murray.
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The 20-year-old is playing under multiple forms of pressure, including the threat of an ATP ban if he draws a warning on court.
The potential penalty stems from his August run-in at Montreal with Stan Wawrinka, in which Kyrgios insulted the French Open winner and his girlfriend.
The ATP fined the Kyrgios $US25,000 ($A35,600) dollars and put him on behaviour notice through to February 24.
He was also dropped from the Australian Davis Cup team, which lost a semi-final last weekend in Scotland to Britain.
In addition, he is playing at "home", with his mother a Malaysian and her son considered almost a native by local tennis fans.
Kyrgios crashed out in the first round in the capital a year ago.
"It's definitely a special tournament not only for me, but also my mum," said Kyrgios, who is accompanied by his parent.
"I also have a lot of relatives in Malaysia so there is added pressure for me to do well. But I enjoyed playing in KL last year and felt really comfortable. I think I can do well in Malaysia.
"The courts (surface) are perfect, they are quite similar to the Australian Open and I think it suits my game a lot."
Spain's David Ferrer heads the seventh edition of the tournament, with the veteran chasing a London spot and stands provisional eighth.
Seeded second is compatriot Feliciano Lopez, with Croatian wild card Ivo Karlovic third ahead of Bulgarian Grigor Dimitrov and No.5 Serb Viktor Troicki.
