Top seed David Ferrer made an encouraging start to the defence of his Valencia Open crown as he eased past France's Gael Monfils in straight sets.
The local favourite, who is looking for his fourth victory at the event in his home town, came through 6-3 6-2 to set up a second round clash with another Frenchman, Julien Benneteau.
Although he dropped his own serve, two breaks were enough for Ferrer to take the opening set and Monfils then appeared to be struggling physically in the second.
Ferrer showed no mercy and two further breaks were enough to wrap up a straightforward victory for the world number three.
The 31-year-old Spaniard claimed afterwards that Monfils' apparent injury had not distracted him, stating: "I tried to concentrate on my game because often when you see that someone has a physical problem you stop hitting so hard."
It was not such a profitable day for another former champion as Marcel Granollers crashed out in straight sets to Fabio Fognini, the dangerous Italian also winning 6-3 6-2.
Philipp Kohlschreiber caused a minor upset as he came through an enthralling three-setter to beat compatriot, and second-seeded Tommy Haas, 3-6 6-3 6-3.
Fourth seed John Isner of the United States came through a big-hitting contest with Latvia's Ernests Gulbis, progressing via two tie-breaks 7-6 (7/4) 7-6 (7/2).
Elsewhere, Jeremy Chardy beat Florian Mayer 4-6 7-5 6-3, while Jarkko Nieminen was a comfortable victor over Benoir Paire as he triumphed 6-3 6-3.