Nicolas Mahut made a successful start to his title defence at the Rosmalen Grass Court Championships on Monday, while Steve Johnson came from a set down to reach the second round of the Mercedes Cup.
American Johnson, the fifth seed, overcame German wildcard Maximilian Marterer 3-6 7-6 (7-2) 6-4 at the ATP 250 grass court event in Stuttgart.
Mischa Zverev, seeded sixth on home soil, brushed aside Malek Jaziri 6-3 6-1. There were also straight-sets wins for Yannick Hanfmann and Jan-Lennard Struff.
In 's-Hertogenbosch, Aljaz Bedene  and Mahut  got the better of Denis Istomin and Dennis Novikov respectively.
Bedene had to mount a comeback to triumph 3-6 6-2 6-1, while Mahut, the 2013, 2015 and 2016 champion, was a 6-3 6-4 winner, making it 14 victories in succession at what is clearly one of his favourite venues.
Andreas Seppi needed three sets to get past Tatsuma Ito, while Vasek Pospisil ousted Tallon Griekspoor.