GENEVA (AP) Sixth-seeded Federico Delbonis of Argentina beat Janko Tipsarevic 6-1, 7-6 (6) on the Serbian's return from an eight-month injury absence at the Geneva Open on Monday.
Tipsarevic, a former No. 8, is ranked 686th after not playing consistently injury-free since 2013.
Seventh-seeded Steve Johnson of the United States beat Mikhail Youzhny of Russia 6-3, 7-5 to score a first clay-court win this season at his fourth attempt.
Eighth-seeded American Sam Querrey fell to a 7-6 (5), 6-4 loss against clay specialist Guillermo Garcia-Lopez of Spain.
Another former top-10 player, Ernests Gulbis of Latvia won against Ricardas Berankis of Lithuania 7-5, 7-5.
Top-seeded Stan Wawrinka, in a final warmup event before defending his French Open title, plays a second-round match on Tuesday against Spain's Albert Ramos-Vinolas.