Johanna Konta breezed through her opening match at the Western & Southern Open, two weeks after suffering heart palpitations during a tournament in Kentucky.
The British number one was a 6-2 6-0 winner over Kirsten Flipkens in the last 32 in New York, advancing without facing a single break point in the match.
The 29-year-old was competing just a fortnight after she had to seek medical help during her first-round exit at the Lexington Open, in what was her first competitive match since lockdown began in March.
Marie Bouzkova produced an impressive performance to shock No.3 seed Petra Kvitova, recovering from the loss of the first set to seal a 2-6, 7-5, 6-2 victory in two hours 25 minutes.
Holding a 5-7 record against Top 20 players ahead of the meeting against the WTA World No.6, she was forced to ride out a storm for the opening set-and-a-half but sufficiently withstood the barrage of winners to overcome an opponent who was playing in her first tournament since making the final of Doha in the early spring.
Meanwhile, Dan Evans was beaten in straight sets by Milos Raonic in the second round of the men's tournament.
The 2016 Wimbledon finalist hit 23 aces on his way to recording a 6-3 7-5 victory.
Third seed Daniil Medvedev launched the defence of his title with a tidy 6-4 6-4 second round win over Marcos Giron, getting his US Open preparations off to an upbeat start.
The subdued atmosphere and empty stands at the Billie Jean King National Tennis Center were far removed from a year ago when Medvedev entertained a capacity crowd with a startling fight back in the US Open final against Rafa Nadal before falling to the Spaniard in five-sets.
The Russian world number five will next take on Slovenian qualifier Aljaz Bedene, who was 7-6 (5) 7-5 winner over American Taylor Fritz.