Tenth seed Marin Cilic eased into the second round of the Shanghai Masters with a straight-sets victory on Monday as Grigor Dimitrov set up a clash with second seed Novak Djokovic.
Croatian giant Cilic, who stands 6 feet 6 inches (198 cm) tall, beat Lukasz Kubot 7-5, 6-3, hitting eight aces and breaking his Polish opponent four times.
Bulgaria's Dimitrov defeated Pablo Andujar of Spain 7-5, 6-3 but faces a daunting task against Djokovic, fresh from victory at the China Open and aiming to displace Roger Federer at the top of the rankings.
Sam Querrey of the United States fired 11 aces in a 6-3, 6-1 victory over Chinese wildcard Zhe Li.
"I feel like I'm playing better now than a year and a half ago when I was ranked number 17," said Querrey, now ranked 26th.
"I'm more confident," he added. "Felt good out there today. It was fun to play in that stadium. I thought I served great. I thought I returned well and I took advantage of the break points. That was the key."
Frenchman Benoit Paire defeated German qualifier Philipp Petzschner 7-6 (7/2), 6-4 to set up a second-round meeting with compatriot Jo-Wilfried Tsonga, the fifth seed.
The number one ranking is on the line at the Shanghai Masters.
Federer can guarantee his place as number one by reaching the quarter-finals but anything less and Djokovic would overtake the Swiss by winning the Shanghai crown.
Federer is beginning his 299th week as world number one, having usurped Djokovic at the top of the leaderboard after winning his 17th Grand Slam title at Wimbledon.
There were also wins on Monday for Spain's Tommy Robredo and Kevin Anderson of South Africa.