Sierra, who grew up playing on clay, broke Raducanu’s serve in the opening game, and things went downhill from there for the Briton.

Raducanu hit 15 unforced errors to zero winners as Sierra broke twice more on her way to a first-set ‘bagel’.

A downcast Raducanu took time off court before returning for the second set, and while she managed to get a game on the board early on, it remained plain sailing for Sierra, who put away a series of booming forehand winners to storm to a 4-1 lead.

A break back gave Raducanu a glimmer of hope and belief started to creep in when she levelled the set at 5-5 with Sierra serving for the match.

Sierra broke back immediately but once again failed to serve out the win as a resurgent Raducanu forced a tie-break.

However, after clawing her way back to 5-4 from 5-1 down in the tie-break, Raducanu’s resistance let up and Sierra secured victory after an hour and 45 minutes.

Raducanu has been blighted by illness and injuries in recent years and has only gone beyond the third round of a major once since her US Open win in 2021.

Her focus will now turn to the British grass-court season as she continues to work with coach Andrew Richardson, who helped guide her to the Flushing Meadows title as a teenage qualifier and was re-hired by Raducanu earlier this month.

Sierra will face either Italian 13th seed Jasmine Paolini or Dayana Yastremska of Ukraine in the second round.