World number 85 Lukas Rosol booked a clash with US Open champion Stan Wawrinka with victory in the first round at the St Petersburg Open.
The Czech saw off Argentina's Diego Schwartzman 6-4 6-4 in the Russian event to set up a last-16 meeting with top seed Wawrinka, who received a bye.
Also joining Wawrinka and the two other top-10 players to avoid early action - Milos Raonic and Tomas Berdych - was Germany's Alexander Zverev, the 19-year-old fifth seed. Zverev, ranked 27, beat Russian wildcard Karen Kachenov 7-6 6-4.
In the other first-round match to take place on Monday, Ricardas Berankis of Lithuania overcame Frenchman Adrian Mannarino 7-6 3-6 6-3.
At the Moselle Open in Metz, veteran Frenchman Julien Benneteau - a wildcard - surprised fifth seed Martin Klizan of Slovakia 6-2 6-1.
Gilles Muller of Luxembourg was also victorious in France, beating Argentinian Horacio Zeballos 7-6 7-5. World number 10 Dominic Thiem, who was handed a bye, is the top seed.
Source: PA