Top seed David Ferrer began his bid for a third straight Copa Claro title in Buenos Aires with a straight sets win over Argentinian Maximo Gonzalez.
But it was far from straightforward for the Spaniard, playing his first match since the Australian Open quarter-finals, as he needed just over two hours for his 7-6 (9-7) 6-4 victory.
Both players lost their serve twice during the mammoth first set before the tense tiebreaker. Gonzalez survived three set points before the Spaniard took the set.
The 31-year-old Ferrer then broke twice in the second set before serving out the match.
Meanwhile, sixth seed Robin Haase was pushed hard by another Argentine, Martin Alund.
Haase's 6-4 6-7 (6-8) 6-3 win saw a comeback by Alund in the second set when he won the tiebreak. But the Dutch player proved too strong for Alund in the third set, breaking his serve at a crucial moment.
Argentine Juan Monaco lost to Albert Ramos 6-7 (3-7) 6-4 6-2 and Santiago Gilrado defeated Albert Montanes 7-6 (7-4) 62.
Second seed Fabio Fognini eased through the round of 32 with a 7-5 6-2 winner over Julian Reiser in Argentina.