Champion in 2016, Kerber's title defence ended almost before it began 12 months ago with the German suffering a 6-3 6-1 first round shellacking by Japan's 46th ranked Naomi Osaka.
Fourth seed Angelique Kerber showed that she has fully recovered from last year's US Open hangover by disposing of Russian Margarita Gasparyan 7-6(5) 6-3 on Tuesday to reach the second round at Flushing Meadows.
Champion in 2016, Kerber's title defence ended almost before it began 12 months ago with the German suffering a 6-3 6-1 first round shellacking by Japan's 46th ranked Naomi Osaka. That upset provided a sobering reminder that anything can happen at a grand slam and Kerber made sure she would not be caught with her guard down again this year as she took on a player making her US Open main draw debut.
A three-time Grand Slam winner against an opponent sitting at 370 in the world rankings and making her first appearance in a major in more than two years would appear a mismatch but it was a contest Kerber approached in a business-like manner.
Despite the background Gasparyan, who has a WTA Tour title on her resume, represented a potentially tricky first round opponent, returning to the circuit this season after missing 15 months recovering from a career-threatening knee injury.
"This is the first time that we played against each other, and she was really hitting the balls really good, really clean," said Kerber. "I knew that she was injured for a long time... Now she's coming back. If she's playing like this in the next weeks and months, for sure, she (will) soon (be) really high in the rankings."
The Russian showed some of her potential and a fair amount of grit by battling to take Kerber to a first set tiebreak but the Wimbledon champion kept her cool on a sweltering day on Louis Armstrong Stadium court to prevail 7-5.
The 23-year-old Gasparyan refused to wave the white flag and broke Kerber to open the second set, but the German broke back immediately to slowly seize control and wrap up the match. "It was really not easy out there today," said Kerber. "I think it's one of the hottest days that I remember here. But at the end, when you're out there, you just try to survive a little bit."
Ostapenko battles through
Jelena Ostapenko sweated out a 6-4 4-6 7-5 win over German Andrea Petkovic to reach the second round of the US Open on Tuesday as the heat was turned up at Flushing Meadows.
With the thermometer pushing towards 100 Fahrenheit (38 Celsius) the pair battled for two hours and 18 minutes under a ferocious sun before the 10th seeded Latvian ended the marathon on her fourth match point, sending the few remaining spectators at the Louis Armstrong Stadium court scrambling to find shade.
"Today (it) was a very tough match. She (Petkovic) was fighting for every point until the end," said Ostapenko, who will meet American Taylor Townsend in the second round. "I mean, of course conditions were difficult today. It was very humid and also very hot, but it was the same for both of us. I mean, we had to deal with it."
Petkovic, having failed to qualify in Cincinnati and New Haven ahead of the US Open, arrived at Flushing Meadows well rested and the 30-year-old needed all her reserves on a sweltering day that is sure to test the fitness of every player across the sprawling Billie Jean King National Tennis Center.
Ostapenko, the 2017 French Open champion, may have also benefited from an uninspiring build-up to the season's final grand slam, crashing out in the first round at Montreal and Cincinnati to leave her fresh going into her opener.
Still, the conditions were so oppressive that officials implemented the extreme weather rule, sending the players off the court for 10 minutes to get out of the heat. "I think it helped me a lot," said Ostapenko. "I went, actually, to the bathroom and changed the outfit for the new one to be more fresh and just stayed in air conditioning. I think it helped me, because then I went back on court and I broke her serve straightaway."
As the score indicates, there was little to choose between the two players, Ostapenko hitting 97 winners to Petkovic's 94. "It's very important to win those tough matches because first rounds are always tricky," said Ostapenko. "It's very important to win the match when you're not playing your best probably. It gives you more confidence."
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 "Angelique Kerber in action on Tuesday")
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