The first day of the U.S. Open ended in heartbreaking fashion for one American, as former tournament champion Sloane Stephens blew a sizable lead en route to another first-round exit.

Stephens won her first set, 6-0, against Clara Burel and led the second, 3-0, before the latter came rallying back Monday night at Arthur Ashe Stadium in Queens.

Burel won the second and third sets by a score of 7-5, despite trailing 5-4 in both.

The French-born Burel repeatedly broke Stephens’ serves to complete her improbable comeback. Burel is set to face Victoria Azarenka of Belarus in the second round on Wednesday.

Stephens, 31, won the U.S. Open in 2017 but has not advanced past the quarterfinal since. That 2017 title remains the Florida-born Stephens’ lone Grand Slam win.

Monday marked Stephens’ fourth first-round exit out of 13 times competing at the U.S. Open. She lost in three sets to Beatriz Haddad Maia in the opening round last year.

This year’s loss came hours after fellow American — and defending U.S. Open champion — Coco Gauff cruised to a 6-2, 6-0 win in the first round against Varvara Gracheva.

Gauff, who is also from Florida, endured a summer slump, dropping difficult matches at the French Open and the Olympics before being upset in the first round of the Cincinnati Open — a tournament she won last year — by unranked Yulia Putintseva this month.

“The last couple of weeks were tough, and I was like, ‘I have to do this and do that, but I don’t have to prove anything to anyone except myself,’ ” Gauff, 20, said Monday.

“I have many more years coming back here and I’m not going to win every year,” she said. “Just that perspective and just having the belief that I can — but not the expectation that I should.”

With News Wire Services