Andy Murray began his Rotterdam mission with a satisfying straight-sets win over French player Edouard Roger-Vasselin.
The Scot won 6-3 6-3 in an hour and a half at the Ahoy venue where he is attempting to be champion for a second time, having beaten Rafael Nadal in the 2009 final.
It was not a classic performance from Murray, but he comfortably had enough to see out the job.
Having returned from back surgery, Murray has reached the Australian Open quarter-finals and helped Great Britain through to the Davis Cup quarter-finals already this season.
Tommy Haas followed his run to the Zagreb final with a battling first-round win.
German veteran Haas had an impressive week in Zagreb and went straight from there, where he lost out to Marin Cilic for the silverware, to this week's Dutch venue and a tricky opener against Spain's Fernando Verdasco.
Haas, 35, was competing at the Rotterdam event for the first time and slugged it out with Verdasco for two-and-a-half hours before coming through a 6-7 (4/7) 7-6 (7/1) 7-5 winner, to set up a clash with Jerzy Janowicz in the second round.
"It was a tough match. I had a couple of chances in the first set, up a break and then in the tie-break," sixth seed Haas said on atpworldtour.com. "I felt I got a little unlucky, when he took it. I did well to recover a break in the third set, so I am pleased that I stayed with him."
Top seed and defending champion Juan Martin del Potro also overcame a potentially awkward opponent as the Argentinian beat Frenchman Gael Monfils 7-6 (8/6) 6-3.
Monfils' compatriots RIchard Gasquet and Nicolas Mahut survived the opening round. Fourth seed Gasquet edged out Dutchman Thiemo de Bakker 67(5/7) 7-6 (7/2) 6-3, and Mahut was a 7-5 6-3 winner against German Daniel Brands.
Austrian Dominic Thiem got the better of Finland's Jarkko Nieminen by a slender 6-4 4-6 6-4 margin, setting up a clash with Murray.