Thiem, who ended Rafael Nadal's 50-set winning run on clay at the Madrid Open, is the top seed in Lyon as he gears up for the French Open - and he had few problems in his tournament opener.

The Austrian was a 6-2 6-4 winner against Roberto Carballes Baena in 71 minutes, the nine-time ATP World Tour champion setting up a clash with another Spaniard, Guillermo Garcia-Lopez.

Joao Sousa, the only other seeded player in action in Lyon, fell by the wayside, though, as the Estoril Open winner lost to qualifier Filip Horansky to hand him his first Tour victory.

At the Geneva Open, rain postponed Wawrinka's match with Jared Donaldson - his second fixture since returning from injury - until Wednesday.

There were shocks elsewhere, with David Ferrer beaten by Peter Gojowczyk, as Marton Fucsovics thrashed Albert Ramos-Vinolas 6-1 6-2.

Steve Johnson, who beat Wawrinka at the Internazionali d'Italia, came through unscathed against Marius Copil.