Top seed Kei Nishikori was tested by a stubborn opponent before finally putting away Pierre-Hugues Herbert 3-6, 6-1, 6-4 on Tuesday at the Rotterdam Open.
Croatia dethroned holders France to win the Davis Cup for the second time as Marin Cilic beat Lucas Pouille in straight sets to seal the victory.
Adrian Mannarino sent defending champions France through to the Davis Cup quarter-finals on Sunday after sealing victory over the Netherlands, while Croatia knocked off Canada to follow Spain through.
Only two seeds remain at the Qatar Open after two more were beaten in the tournament's early matches on Wednesday, leaving six of the event's eight highest-ranked players out with only half of the second round completed.
The Qatar Open second and third seeds -- Spain's Pablo Carreno Busta and Tomas Berdych of the Czech Republic -- crashed out of the tournament in the first round on Tuesday on a night of shocks in Doha.
Lucas Pouille throttled Belgium's Steve Darcis 6-3, 6-1, 6-0 in Sunday's decisive fifth rubber to clinch a 10th Davis Cup title for France in front of a passionate Lille crowd.