The 20-year-old Sabalenka, who is ranked No. 20 and is one of the most promising young stars on the WTA Tour, was the only player to take a set off of eventual champion Naomi Osaka at the just-concluded US Open in New York, reports Efe news.
But Lepchenko pulled off the upset on Tuesday, thanks to her success on the big points.
The 110th-ranked American saved all three break points she faced in the first set and then in the second set fought off a determined comeback bid by Sabalenka, who rallied from a break down and also nearly came back after trailing 0-4 in the tiebreaker.
Two other seeded players also crashed out in the first round.
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