Roberta Vinci, the 2015 runner-up, and two-time Wimbledon champion Petra Kvitova booked US Open third round spots on Wednesday as Novak Djokovic and Rafael Nadal prepared for the latest tests of their battle-scarred seasons.
Seventh seeded Italian Vinci, defeated by compatriot Flavia Pennetta in last year's final, eased past Christina McHale of the United States 6-1, 6-3.
The 33-year-old, playing at Flushing Meadows for the 14th time, goes on to face either Yulia Putintseva of Kazakhstan or Germany's Carina Witthoeft.
Kvitova, the 14th seeded Czech who recorded her best performance in New York 12 months ago when she made the last-eight, beat Turkey's Cagla Buyukakcay 7-6 (7/2), 6-3.
Kvitova was in her trademark all-or-nothing mood, mixing up 31 winners with 30 unforced errors against her 26-year-old opponent who was the first Turkish woman to play in the main draw at the tournament.
Up next for Kvitova is Ukrainian 22nd seed Elina Svitolina who put out Lauren Davis of the United States 6-1, 4-6, 6-3.
Later on Wednesday, defending champion and world No 1 Djokovic, who needed treatment on a right upper arm injury during his laboured four-set win over Poland's Jerzy Janowicz on Monday, faces Jiri Vesely of the Czech Republic.
Vesely inflicted a rare defeat on the Serb when he triumphed on clay at Monte Carlo in April.
"Different surface, different circumstances, best-of-five. But still, Vesely deserves respect," said Djokovic, the 2011 and 2015 champion in New York and looking for a third major of the year.
"He has a big game, big serve, big forehand, and moves well for his size. So let's see. Conditions are quite suitable to my style of the game. Hopefully I'll be able to slow his serve down a little bit and then take it from there."
NADAL IN ACTION
Spanish fourth seed Nadal, the 2010 and 2013 champion, takes a 7-1 career record over Italy's Andreas Seppi into their night time clash.
Seppi, ranked at 87, has never got beyond the third round in New York but he is a former top 20 player who knocked Roger Federer out of the Australian Open two years ago.
Like Djokovic, Nadal is suffering the after-effects of injury after a serious problem with his left wrist sidelined him from midway through the French Open until the Rio Olympics.
Reigning Roland Garros champion and third seed Garbine Muguruza of Spain tackles Latvia's Anastasija Sevastova.
Muguruza needed three sets to see off Belgian qualifier Elise Mertens in a first round tie which also saw her need a medical timeout after suffering heat exhaustion.
Angelique Kerber, the second seeded Australian Open champion who could depose Serena Williams as world No 1, faces 34-year-old Mirjana Lucic-Baroni.
The veteran Croatian made the last 16 in 2014 having played her first US Open back in 1997.
Two highly fancied potential title winners are also in second-round action.
Canadian fifth seed Milos Raonic, the Wimbledon runner-up, plays Ryan Harrison of the US.
In the women's draw, American eighth seed Madison Keys meets 16-year-old compatriot Kayla Day.