British duo Johanna Konta and Cameron Norrie suffered early exits from the Western & Southern Open in Cincinnati on Tuesday.
Konta suffered a rain-interrupted 3-6 7-6 (7-5) 6-2 loss to Karolina Muchova in the first round, despite winning the opening set in style.
Norrie, who had a chance of becoming the new men's British No 1 with a run to the quarter-finals, will have to wait a little longer after being beaten by big-serving American John Isner.
Qualifier Heather Watson must wait to take to the court against top-ranked Ashleigh Barty after their match was postponed due to two rain delays.
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British No 1 Konta, who withdrew in the third round at Montreal last week due to a knee injury, made an assured start and, aided by some lovely forehand strokes, took the opening set.
Rain then interrupted the second set in Ohio, where the 30-year-old squandered three break points at 1-1 with missed returns, before Czech Muchova levelled up the match by winning a close tie-break.
The 24-year-old took the deciding set comfortably and will face former US Open champion Bianca Andreescu in round two.
Norrie started strongly in his first-round encounter against John Isner before being knocked out of the tournament by the 2013 runner-up.
The American, who moved to 2-1 overall against Norrie with the win, dropped the first set to the 25-year-old but battled back and smashed 25 aces for the match to claim a 4-6 7-6 (7-5) 6-4 victory.
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Emma Raducanu set up a second-round clash with former junior world No 1 Clara Burel following an upset win over Belgian top seed Alison van Uytvanck at the Chicago 125 tournament.
The 18-year-old Briton, who earlier this year reached the fourth round of Wimbledon in just her second professional tournament, was a 7-6 (9-7) 6-3 victor over the world No 60.
Raducanu's compatriot Harriet Dart, meanwhile, was bundled out of the competition's first round 6-1 6-7 (2-7) 6-2 by Denmark's Clara Tauson.
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