Rios, the world No 6, had been forced to withdraw in the second set of his final against Sweden's Thomas Enqvist in Marseilles last Sunday because of a strained thigh muscle. But the Chilean was declared fit after treatment and produced near flawless tennis in the first set of a match which featured some breathtaking rallies.
Rios fell 2-0 behind early in the second set, but quickly fought back to take the match in just over one hour. Rios is now the favourite in Antwerp after Goran Ivanisevic, the top seed, pulled out of the tournament late on Tuesday with tendinitis in his shoulder. The Croat withdrew only hours after the fourth seed, Boric Becker, had dropped out of the event with a wrist injury.
The third seed, Thomas Enqvist of Sweden, was later added to the long list of early exits, losing in the opening round to Francisco Clavet of Spain. Clavet's patience wore down the world's No 8 to win 4-6, 7-6, 6- 3.
Tim Henman, the No 6 seed, may be able to exploit the gaps in the draw. The Briton plays Mikael Tillstrom today although the Swede is another player not fully fit - he has flu. The tournament has also lost its No 8 seed, Jan Siemerink, who had hamstring trouble and was beaten in the first round by a qualifier. Michael Stich, the defending champion, another first-round loser, had shoulder problems.