Juan Martin del Potro is out of the Delray Beach Open after a three-set, quarter-final defeat to USA star Mackenzie McDonald.
Argentine ace Del Potro is on the comeback trail after yet more injury woe but his trip to Florida has come to an end at the last-eight stage, with a 6-4 3-6 7-6 (7-5) loss to the world number 84.
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The former US Open winner was top seed for the tournament despite playing in his first event since suffering a broken kneecap at the Shanghai Masters in October.
In a contest that became tight as it progressed, he bounced back from a one-sided, opening-set loss to level affairs but could not get the job done in the final-set tie-break, with McDonald setting up a semi-final encounter against Moldova’s Radu Albot.
“It’s hard to win matches when you can’t move at 100%,” said Del Potro.
Britain’s Dan Evans faces home favourite John Isner in the other last-four clash in the Birmingham-born star’s first ATP Tour semi-final for more than two years.