Top seed Marin Cilic made quick work of Greece's Stefanos Tsitsipas on Monday, winning 6-3, 6-2 to reach the second round of the Japan Open.
The towering Croatian, runner-up to Roger Federer at this year's Wimbledon, took just 73 minutes to complete a one-sided victory in Tokyo against a player ranked 110 places below him.
World No 5 Cilic, a former US Open champion, rifled eight aces and totally dominated on serve on a speedy hardcourt surface that suits his power game.
"He's a good player, an upcoming star of men's tennis, who forced me to find my best level and a good rhythm," said Cilic, who won 24 of his 29 first service points and is looking to cement his place at the season-ending ATP Tour Finals in London.
"At the end I was pleased with the way I served and how I played," added Cilic, a semifinalist in Tokyo last year.
South African Kevin Anderson, who was beaten by Rafael Nadal in the US Open final last month, also advanced in straight sets, ousting Frenchman Gilles Simon 6-2, 7-6.
Fifth seed Anderson cracked 17 aces as he set up a meeting with American Ryan Harrison, a 6-4, 4-6, 6-4 winner over teenage Japanese qualifier Yusuke Takahashi.
Elsewhere, controversial Australian Bernard Tomic recovered from a wobble to beat Portugal's Joao Sousa 6-3, 3-6, 6-3 in his first match since June, while Frenchman Adrian Mannarino dumped out another local favourite, Go Soeda, 7-5, 7-6.
The Japan Open has been played since 1972 and its previous winners include a roll-call of the game's greats, including Ken Rosewall, John McEnroe, Pete Sampras, Federer and Nadal.