Daniil Medvedev started his grass-court season with victory over Gilles Simon in the Rosmalen Grass Court Championships, while Hubert Hurkacz and Denis Shapovalov suffered shock defeats in Stuttgart.
Medvedev will replace Novak Djokovic at the top of the rankings next Monday and the Russian could celebrate by claiming a first title of the year in ‘s-Hertogenbosch.
The top seed, who will not compete at Wimbledon due to a ban on Russian and Belarusian players, beat Frenchman Simon 7-5 6-4 on Thursday after saving three set points and storming back from 5-2 down in the opener, setting up a quarter-final against lya Ivashka.
Felix Auger-Aliassime, the second seed, defeated Tallon Griekspoor 7-6 7-6, but third seed Taylor Fritz was beaten by wildcard Tim van Rijthoven in straight sets.
Alex de Minaur and Jenson Brooksby also made early exits, losing to French duo Adrian Mannarino and Hugo Gaston respectively.
Marton Fucsovics claimed the scalp of third seed Hurkacz to reach the last 16 at the Stuttgart Open, winning 7-5 6-7 6-3
Shapovalov also lost his opening of the grass-court season, Oscar Otte getting the better of the fourth seed 7-6 7-6.
There was no such trouble for top seed Stefanos Tsitsipas, who beat Dominic Stricker 6-3 6-4, and Andy Murray accounted for seventh seed Alexander Bublik in straight sets.