The second-seeded Nadal was leading 6-2, 6-2 when France's Nicolas Mahut retired with an abdominal muscle injury in the first game of the third set at Arthur Ashe Stadium. The Spaniard committed only five unforced errors and saved all four break points he faced.
The fourth-seeded Murray fought back to upend Haase 6-7 (5-7), 2-6, 6-2, 6-0, 6-4. It marked the sixth time the Scot had won a match after dropping the first two sets.
Murray will battle 25th-seeded Spaniard Feliciano Lopez in the third round. Lopez advanced with a 5-7, 6-4, 7-6 (7-3) 7-6 (7-5) win over Canadian Vasek Pospisil.
Del Potro, the 2009 U.S. Open champ is slowly returning to form after a wrist injury cost him most of the 2010 campaign. He is seeded 18th this year and followed up an easy opening-round win over Italy's Filippo Volandri with a 6-2, 6-1, 7-5 triumph over fellow Argentine Diego Junqueira.
A pair of seeded players lost in five sets on Friday. No. 14 Stanislas Wawrinka of Switzerland fell to American Donald Young 7-6 (9-7), 3-6, 2-6, 6-3, 7-6 (7-1) and Russian Igor Kunitsyn defeated 17th-seeded Austrian Jurgen Melzer 3-6, 6-3, 1-6, 6-2, 7-6 (7-5).