Sixth seed Juan Martin del Potro eased past German Benjamin Becker 6-2 6-4 6-2, while French seventh seed Jo-Wilfried Tsonga battled to a straight-sets win over Japan's Go Soeda.
Meanwhile, former world No. 1 Rafael Nadal will make his long-awaited return to action at the Chile Open in Vina del Mar early next month.
Spain's 11-time grand slam winner has not played since injuring his knee at Wimbledon last June, and had to delay his planned comeback in Melbourne after suffering an illness in December.
Nadal will also play in another South American clay-court tournament, the Brazil Open starting on Feb. 11, as he seeks to regain fitness ahead of his French Open title defense.