Veronelli brushed aside Victor Hanescu, 6-4, 6-2, and is a win away from an unlikely semifinal berth.
No. 4 Filippo Volandri of Italy was forced to pull out of his match with Franco Squillari of Argentina due to a leg injury.
Squillari's next opponent is sixth seed Alberto Martin, who advanced when fellow Spaniard Galo Blanco retired with a shoulder problem.
Also Thursday, eighth seed Luis Horna of Peru ousted 1998 champion Mariano Puerta of Argentina, 6-4, 6-2, to set up a quarterfinal showdown with unseeded Spaniard Oscar Hernandez, a 7-6 (7-3), 6-3 victor over Italian qualifier Tomas Tenconi.