Li, who had a first-round bye and a walkover in the second round after her opponent withdrew, looked out of sorts during a 6-2 6-4 loss to number 10 seed Samantha Stosur played during a power outage that kept the main scoreboard dark for an hour.
"At the beginning of the match I was like - I didn't even know what I should do on the court, not like during the clay court season," Li, seeded sixth, said.
"I know exactly if I hit the ball next here, I come back, what I should do. But I was feeling like a junior on the court.
Li, playing in her first match since a shock exit in the second round of Wimbledon, had five double faults in another day of windy conditions, struggled with the high bounce of Stosur's serve and was unable to break her opponent.