Jared Donaldson suffered a shock straight-sets defeat to Sergiy Stakhovsky in the first round of the European Open in Antwerp on Monday, while Borna Coric made an early exit in Moscow.
World number 52 Donaldson lost 7-6 (7-4) 6-4 to his Ukrainian opponent, ranked 102nd, who joined Ivo Karlovic - 3-6 7-5 7-6 (12-10) victor over Guido Pella - in the second round.
Julien Benneteau benefited from the retirement of Nikoloz Basilashvili from their encounter after winning the first set, while Ruben Bemelmans will face Nick Kyrgios in the next round following his 4-6 7-6 (7-5) 7-6 (7-2) result against Peter Gojowczyk.
In the Kremlin Cup, Dudi Sela got the better of Coric, winning 6-3 6-2, and there were also victories for Yuki Bhambri and Alexander Bublik.
Kazakhstan's Bublik faces second seed Albert Ramos-Vinolas in the next round.