Stefanos Tsitsipas began the Dubai Championships with a 7-6 (7/1), 6-1 victory over Pablo Carreno Busta on Tuesday just two days after winning the Marseille title.
The Greek cruised to a first-round victory in 94 minutes but then complained that the match had been more of a struggle than it looked.
"I was tired," said the world number six who beat Felix Auger-Aliassime in Marseille on Sunday. "I came into the match tired. I was upset with myself a little bit, but I realised I have to save that energy. The physical part was difficult for me.
"I tried to stay calm and not complain too much because I would definitely need that energy for later on. I think I focused on my breathing, constructing the points, staying in the point, trying to make things happen from my backhand side."
Carreno Busta broke early in the first set but Tsitsipas forced a tiebreaker which he won comfortably. He rode that momentum to a blistering second set sweep.
"I'm not pushing myself to the limits like I did last year," said Tsitsipas. "I'm trying to be smarter in the way I handle certain situations and moments in the match."
Tsitsipas, the losing finalist here a year ago to Roger Federer, will next play Alexander Bublik after the Kazakh beat Poland's Hubert Hurkacz 6-2, 7-5.
- Paire escape act -
In the opening match of a day played in desert conditions in which temperatures reached 29 degrees Celsius (82.4 degrees fahrenheit), Benoit Paire fought off four match points to overhaul former US Open winner Marin Cilic 2-6, 7-5, 7-6 (7/1).
Eighth seed Paire appeared all but finished as Croatian Cilic, leading 5-3 in the second set after taking the first, served for a straight sets win.
But the Frenchman broke and won the set.
"Normally when it's one set, 5-3, I normally tank," Paire said. "This time I tried until the end. It was working good. I'm really happy about the win."
Fourth seeded Italian Fabio Fognini, making his Dubai debut, was knocked out after nearly two and three-quarter hours by Dan Evans.
The Briton sealed a 3-6, 6-4, 7-5 victory on his sixth match point after an eight-minute final game which ended as a return on the Fognini baseline was called good by the Hawk-Eye system.
"It's difficult to play Fabio, he's such a class player," Evans said of the world number 11. "It felt like he was on top forever really, I was just hanging in."
Other Tuesday winners included qualifiers Dennis Novak of Austria and Japan's Yasutaka Uchiyama.
Filip Krajinovic advanced past Joao Sousa with a 4-6, 6-3, 6-3 comeback. Japan's Yoshihito Nishioka, who lost the Delray Beach final in Florida on Sunday, rushed to the Gulf only to go down 7-5, 6-2 to France's Pierre-Hugues Herbert in the first round.
Stefanos Tsitsipas accelerated away from Pablo Carreno Busta but then complained of tiredness