However, fourth-seeded Swede Robin Soderling was upset.
Del Potro, winner of four ATP World Tour titles in 2008, beat fellow countryman Guillermo Canas, 6-3, 7-6 (7-5). France's Florent Serra defeated Soderling 6-4, 6-7 (1-7), 6-2.
Also, wild card Marcos Baghdatis beat Japan's Kei Nishikori 7-5, 6-3; Latvian Ernests Gulbis beat American Taylor Dent 6-4, 3-6, 6-2; Belgium's Christophe Rochus defeated American wild card Donald Young, 6-4, 6-3; and Austrian Stefan Koubek beat Spaniard Guillermo Garcia-Lopez, 6-2, 6-2.
Americans Andy Roddick, James Blake, Mardy Fish and Sam Querrey join in with opening-round play Wednesday.