Nadal cruised past Argentine qualifier Facundo Arguello 6-4, 6-0 on the clay courts at the famed Buenos Aires Lawn Tennis Club.
The 28-year-old Nadal is now the sole owner of No. 10 on the Open Era match wins list, passing Boris Becker with victory 714.
Juan Monaco, who won here in 2007, upset fellow Argentine and No. 5 seed Leonardo Mayer 6-4, 6-4.
Also on Day 3, third-seeded Pablo Cuevas of Uruguay got past Argentine wild card Guido Andreozzi 7-6 (7-4), 6-1 and Argentina's Federico Delbonis took care of Italian Paolo Lorenzi 6-4, 6-2.
The 2015 Buenos Aires titlist will collect $91,050.