New York: World number two Andy Murray, vying to become just the fourth man to reach all four Grand Slam finals in a calendar year, was made to look ordinary through two sets by Italian journeyman Paolo Lorenzi, but pulled himself together to win 7-6 (7/4), 5-7, 6-2, 6-3.
"I had to stop rushing," said Murray, who arrived at the year's final Grand Slam off victories at Wimbledon and the Rio Olympics and may have expected less from Lorenzi, the 34-year-old who only won a first ATP title in July.
"I was making a lot of unforced errors and (Lorenzi) is very solid, and doesn't give you cheap points," Murray said. "I was looking for those cheap points too often.
"When I slowed down, the unforced errors went down, and the winners went up."
Serena Williams sped past another milestone Saturday as her 307th Grand slam match win took her past Martina Navratilova's record and into the fourth round of the US Open.
Williams dominated Sweden's Johanna Larsson 6-2, 6-1. Not only has she surpassed Navratilova for most Grand Slam wins by a woman, she equalled Roger Federer's mark for men.
"I was really excited to reach 307," Williams said. "It's something I didn't even know about until Wimbledon -- it was like a new goal. That was pretty cool for me.
"Obviously I want to keep that number going higher," added Williams, who will get her chance when she takes on Kazakhstan's Yaroslava Shvedova for a quarter-final berth.
"And what better place to do it than here where it all started," said Williams, who claimed the first of her 22 Grand Slam singles titles at the 1999 US Open.
A 23rd major triumph would take her past the Open Era record she now shares with Steffi Graf and closer to Margaret Court's all-time record of 24.
But the US superstar has been slowed by a right shoulder injury since her Wimbledon triumph.
Her world number one ranking is under threat, with both second-seeded Angelique Kerber and fourth-seeded Agnieszka Radwanska in with a chance of supplanting her before she can break Graf's record of 186 consecutive weeks at the top.
"It definitely feels solid," she said of the shoulder, which didn't appear to trouble her in the one hour she needed to subdue Larsson. "I'm doing a lot of work on it so I can keep it in this position. Definitely not going to stop doing all the rehab and therapy."
Halep hangs on
Hungarian Timea Babos put a scare into Romanian fifth seed Simona Halep, surging back in the second set and taking a 3-1 lead in the third before falling 6-1, 2-6, 6-4.
"I don't know how I came back," Halep said. "I was fighting to the very end for every ball."
Having regained the break to level the third at 3-3, Halep was unable to convert two break points in the eighth game.
But Babos, unable to convert two game points in the 10th, finally surrendered with a whimper with a double fault on match point.
Halep, who fell in the semi-finals to eventual champion Flavia Pennetta last year, will play Spain's Carla Suarez Navarro for place in the quarter-finals.
Suarez celebrated her 28th birthday with a 6-4, 6-3 victory over Russian Elena Vesnina.
Men's eighth seed Dominic Thiem of Austria also enjoyed a birthday win, downing Pablo Carreno Busta of Spain 1-6, 6-4, 6-4, 7-5 on the day he turned 23.
Radwanska eased into the fourth round with a 6-2, 6-3 victory over France's Caroline Garcia.
The Pole will duel for her first quarter-final berth at Flushing Meadows against Ana Konjuh in a rematch of a Wimbledon second-round clash in which Radwanska saved three match points before finally dispatching the Croatian.
Sixth seed Venus Williams, whose seven Grand Slam titles include US Open crowns in 2000 and 2001, opens the night session on Ashe against 26th-seeded Laura Siegemund.
Nick Kyrgios, the 14th-seeded firebrand from Australia, closes the show on Ashe against Illya Marchenko a Ukrainian ranked 47 spots below him.
Elsewhere, men's third-seed Stan Wawrinka took on 64th-ranked Briton Daniel Evans while sixth-seeded Kei Nishikori, the 2014 runner-up, played France's Nicolas Mahut for a place in the last 16.