(CNN) -- Venus Williams was the first former champion to fall on Friday at the U.S. Open.
The American lost an epic encounter with world No. 13 Sara Errani as the Italian came through 6-0 0-6 7-6.
Roger Federer and Maria Sharapova, also former winners at Flushing Meadows, hope to stay the course later on Friday.
Williams, who has rediscovered some of her best form in the build up to the final grand slam of the season, looked down and out as she lost an error-strewn opening set.
But there were cheers from the crowd on Arthur Ashe court when the 34-year-old home favorite won her first game of the match at the start of the second.
It looked like a phoenix from the flames comeback was on from Williams as she overpowered Errani to level at one set all.
The third set saw the pendulum of momentum swing between the two players.
Williams was serving for the match at 5-3 up only for Errani to break back and eventually force a deciding tiebreak.
The breaker was another see-sawing affair but it was the Italian who conjured some brilliant play to wrap up it 7-5 and book her place in the fourth round.
Williams came into Friday's single match on the back off a draining doubles match with her sister Serena.
The 34-year-old, who is dealing with the effects of Sjogren's Syndrome, will turn her attention to that side of the tournament now.
Fairytale in New York
There was a fairytale in New York for qualifier Mirjana Lucic-Baroni as she knocked out second seed Simona Halep 7-6 6-2.
The world No. 121 had once been one of the game's rising stars, reaching the Wimbledon semifinals in 1999.
But her career went into freefall after personal revelations about an abusive childhood.
Lucic-Baroni fled to the United States with her mother and siblings but her promising tennis career was all but over.
"After so many years, it's incredible," the 32-year-old told reporters. "I live for this. Every painful moment has been worth it."