In Saturday's semifinals, del Potro will play doubles specialist Edouard Roger-Vasselin of France, who beat Daniel Brands of Germany 6-3, 4-6, 6-3.
John Tomic, who also coaches Bernard, is barred from tournaments by the ATP and International Tennis Federation.
Monfils had 16 aces to set up a meeting with sixth-seeded Florian Mayer, who defeated another German, Andreas Beck, 6-4, 3-6, 6-1.
Frenchmen Michael Llodra and Paul-Henri Mathieu have joined seven players who pulled out on Wednesday.
Mahesh Bhupathi-Julian Knowle beat Argentine-Spanish duo Leonardo Mayer and Albert Ramos 6-2, 6-7(5), 6-4, 6-2 in two hours and 37 minutes in the first round clash.
Nadal will play a Saturday semi-final against Canadian fifth seed Milos Raonic, who beat Ernests Gulbis 6-2, 7-6 (8/6) and followed up by winning a hard-fought battle with Spanish veteran Tommy Robredo 6-7 (5/7), 6-3, 7-6 (7/2) in almost two and a half hours.
Djokovic is bidding to become the first player in the Open Era to win three consecutive Australian Opens and was in a different league to Mathieu, running through to his 15th straight match win in Melbourne.
Third seed Roger Federer beat Spain's Albert Ramos 6-1, 6-1, 6-1 on Monday to reach the Wimbledon second round.
This, then, is who John Isner is for now: The Marathon Man of Tennis, the guy who plays and plays and plays, for hours on end, until the last set seems interminable.
Veteran Czech Radek Stepanek on Tuesday ended the Madrid Masters run of Australian Bernard Tomic in the first round, with the Queensland youngster exiting 6-2, 7-5.