Montanes fell to 2-4 in six career meetings with Volandri, who pulled off a 6-2, 6-3 win, taking nearly 80 percent of his first-serve points.
Wild card Javier Marti of Spain advanced with a 6-2, 6-4 decision over Frederico Gil of Portugal, moving on to play third-seeded countryman Fernando Verdasco.
Ricardo Mello of Brazil cheered the hometown crowd with a 6-4, 6-2 win over Spain's Pere Riba, advancing to face fourth-seeded countryman Thomaz Bellucci.
Dennis Rodman pledges to end trips to North Korea
Susan Sarandon 'very excited' about daughter's pregnancy