Murray, Wimbledon runner-up and Olympic gold medalist, downed Ivan Dodig 6-2, 6-1, 6-3 to conclude the day's action.
Ferrer defeated Kevin Anderson 6-4, 6-2, 7-6 (7-3) to set up a second-round meeting with Igor Sijsling.
Del Potro took out Florent Serra 6-4, 7-6 (7-4), 6-4 after Serra had replaced David Nalbandian in the draw early Wednesday.
Isner outlasted Xavier Malisse 6-3, 7-6 (7-5), 5-7, 7-6 (11-9) in a match that took almost 3 hours. Malisse was unable to convert two set points in the fourth-set tiebreak.
Isner took part in his 49th and 50th tiebreaks of the season, the most on the ATP Tour. He will next meet Jarkko Nieminen.
No. 8 seed Janko Tipsarevic rallied from two sets down to defeat Guillaume Rufin 4-6, 3-6, 6-2, 6-3, 6-2. Richard Gasquet, the No. 13 seed, also came from behind to oust Albert Montanes 4-6, 6-2, 6-3, 6-3.