Defending Rotterdam Open champion Andrey Rublev and world number four Stefanos Tsitsipas won through their opening tests, but Denis Shapovalov will not be in round two.
Rublev beat Henri Laaksonen 6-4 6-4 on Tuesday, while top seed Tsitsipas went the distance before edging out Alejandro Davidovich Fokina 7-5 6-7 (1-7) 6-4 after two hours and 39 minutes on the court.
Reflecting on his win, Tsitsipas was full of praise for his opponent, saying: “It was a great battle; he gave me some of the best tennis I have seen him play.
“He was very fired up today and making the best out of every single shot. He was hitting huge winners from behind the baseline. He’s one of the best young players who I have played.”
However, world number 12 Shapovalov had no such luck, as he slumped to a surprise defeat to Czech qualifier Jiri Lehecka.
The world number 137 saw off the Canadian 6-4 6-4, showing impressive resolve to hold serve at 4-2 in the first set after initially going 0-40 down.
Shapovalov converted just one of 11 break points offered up by Lehecka as he failed to build on an impressive run to the Australian Open quarter-finals last month.
Aslan Karatsev, who won a title in Sydney in January, was another seed to drop out, after his 2-6 7-6 (7-2) 7-6 (7-0) defeat to home favourite Tallon Griekspoor.
Griekspoor has enjoyed some big wins in this tournament in the past, having defeated Stan Wawrinka and Karen Khachanov in 2018 and 2019 respectively.
Khachanov, too, was in action on Tuesday; unlike his Russian compatriot Karatsev, Khachanov took his place in round two with a 6-7 (4-7) 6-1 7-6 (7-6) defeat of Alexei Popyrin.
Lorenzo Musetti and Dutchman Botic van de Zandschulp also progressed.