Jabeur had complained of a knee problem after her opening victory at Melbourne Park and seemed out of sorts for much of the loss against Vondrousova, which ended a little past 1 a.m. on Friday.
Jabeur, who is from Tunisia, was the runner-up at Wimbledon and the U.S. Open in 2022 and came to Australia considered a contender for what would be her first Grand Slam title.
She reached the quarterfinals in Melbourne in 2020 but missed the tournament a year ago with an injured back.
The left-handed Vondrousova reached the final of the French Open as a teenager in 2019 but has never made it past the fourth round in 17 other appearances at Grand Slam tournaments.
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