Matt Ebden has taken a set off Stefanos Tsitsipas but the world No.11 proved too good for the Australian in their opening round encounter at the ATP Tour's Dubai Championships.
Two days after he lifted the title in Marseille, Tsitsipas overcame world No.47 Ebden 6-4 3-6 6-3 to record his 12th win in 16 tour-level matches this season.
Greek 20-year-old Tsitsipas, who reached the Australian Open semi-finals last month, won 92 per cent of first-serve points to claim victory after one hour and 43 minutes.
Top seed Kei Nishikori overcame ailing Frenchman Benoit Paire 6-4 6-3 to reach the second round.
The world No.6, making his debut in Dubai, saved seven break points in the first set before he took advantage of Paire's troublesome right knee to prevail in 81 minutes.
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"It's never easy playing Benoit. He has a great serve and a great backhand," Nishikori said.
"I think the key was the longest game at 2-1 in the first set... If he broke back, anything could have happened. It was a good match."
Croatian sixth seed Borna Coric was pushed all the way in his 7-5 3-6 7-6 (7-4) win over luckly loser Jiri Vesely.
It wasn't all plain sailing in the opening round for the seeded players with Marin Cilic and Daniil Medvedev crashing out.
Veteran Frenchman Gael Monfils knocked out Croatian third seed and former US Open champion Cilic 6-3 4-6 6-0.
"I have new goals, [a] new team, [a] new routine," 32-year-old Monfils said.
"Obviously, wins under my belt. Everything is going fine. I am just trying to keep doing what I'm doing."
Monfils won his eighth ATP Tour title two weeks ago in Rotterdam.
World No.113 Ricardas Berankis stunned eighth-seeded Russian Medvedev 6-3 6-3.
"I was feeling good today. I'm really happy with my game," 28-year-old Lithuanian Berankis said.
"The plan was to stay as close as possible and not to get in his game, which is to get into those long rallies which he loves."
Twice finalist Tomas Berdych faced a stern test from lucky loser Ilya Ivashka but the Czech veteran pulled off a 6-4 4-6 7-6 (7-4) victory.
Other first-round winners on Tuesday were wildcard Marcos Baghdatis, Hubert Hurkacz, Denis Kudla and qualifier Egor Gerasimov.
