Top seed Richard Gasquet was arriving for his start at the ABN-AMRO World Tennis with the Frenchman hoping to repeat his title success of the weekend in Montpellier.
Gasquet, who takes over the top spot in the field at an event hit hard by the knee meniscus operation to Roger Federer, which took the Swiss drawcard out of the tournament, won his 13th career trophy and will be hoping to keep up his momentum.
The 29-year-old had a late start to 2016 after missing the Australian summer with back problems.
Second seed Marin Cilic, the 2014 finalist against Tomas Berdych took up the slack on opening day as he beat Denis Istomin 7-6 (7-5), 6-4 to leave the Uzbek winless after three losses in as many years at the Ahoy stadium.
The Croatian is coached by famed compatriot Goran Ivnisevic, who won the Rotterdam trophy two decades ago.
"It would be so great to win the title 20 years later in front of Goran," said former US Open champion Cilic.
"To win here would be a huge honour. But the tournament is tough. I can only go step by step, but I will be pushing myself hard to try and win it."
Cilic won in 90 minutes with 10 aces and never faced a break point to improve to 7-1 over Istomin.
"It was a tough, mental challenge," the 13th-ranked winner said. "The first set was very close and the second was a mental battle. I was lucky to pull it through."
Countryman and qualifier Ivan Dodig, ranked 87th, delivered a 6-3, 7-6 (7-4) surprise to French seventh seed Benoit Paire, who has now lost four straight matches dating back a month to Auckland.
He fell victim to more than 50 unforced errors and the match-tougg Dodig won in his third match point and claim revenge for a 2013 loss in Monte Carlo..
Jiri Vesely beat fellow Czech Lukas Rosol 6-4, 6-2.