Rafael Nadal extended his unbeaten run over Frenchman Richard Gasquet to 15 to reach the Cincinnati Open third round.
The Spaniard, 31, who has not lost a set to Gasquet since 2008, won 6-3 6-4.
Roger Federer's withdrawal from the tournament means on Monday Nadal will return to world number one for the first time since July 2014, taking over from Andy Murray who is also injured.
Meanwhile, Alexander Zverev's 10-match winning streak ended with defeat by unseeded American Francis Tiafoe.
Zverev, 20, has moved up to seventh in the world rankings following victory over Roger Federer in Montreal.