Top seed Djokovic, the defending champion and world number two, was among those set to play Thursday but his last 16 match against American Sam Querrey was wiped out along with the other seven singles matches on the schedule.
Djokovic, however, was unruffled by the rain as he walked onto centre court shortly after his 7 p.m. local time match was set to begin and started playing with a squeegee before hitting a few balls while holding an umbrella in his left hand.
With more rain forecast for Friday and possibly into the weekend, tournament organisers could be left scrambling to get matches played in time for Sunday's scheduled final.
The rain was the latest setback for a tournament that has been hit by withdrawals from a handful of players, including world number one Roger Federer and number three Rafa Nadal.
Murray, fresh from his emotional Olympic triumph on Sunday, not so surprisingly pulled out of the tournament with a knee injury a day after calling a medical timeout during which he received about five minutes of treatment.
"I decided the best thing was to rest it and try and make sure I can let my body kind of adjust to the surface normally," Murray, who was scheduled to play Canada's big-serving Milos Raonic in a last 16 match on Thursday, said.
The world number four, who was hurt chasing down a forehand late in his match, blamed the injury on a lack of time to prepare for the switch to hard courts from grass.
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