Teenage dream for Bellis
CiCi Bellis produced the most sensational result of this year's US Open so far as the 15-year-old dumped out Australian Open finalist Dominika Cibulkova in the first round.
The American teenager, who is ranked 1,208th in the world, kept the Slovakian's comeback at bay to secure a 6-1 4-6 6-4 victory.
Bellis secured a wild card for the Flushing Meadows fortnight after winning the USTA girls' national championship.
Despite that promising result and a growing junior pedigree, she was not expected to cause any problems for Cibulkova, who was seeded 12th for the tournament.
But Bellis produced a major shock to become the youngest player to win a singles match in the US Open since Anna Kournikova in 1996.
Two-time finalist Victoria Azarenka managed to avoid an upset as she came back from a set down to defeat Misaki Doi 6-7 (3-7) 6-4 6-1.
Azarenka, who has slipped all the way to 17th in the world rankings after an injury-hit season, made a shaky start but was well in control during the deciding set.
Elsehwere in the women's draw, Wimbledon finalist Eugenie Bouchard eased into the second round with a 6-2 6-1 victory over Olga Govortsova.
Bouchard has reached at least the last four of every grand slam so far this year and made an assured start to her US Open campaign at Louis Armstrong Stadium on Tuesday. The 20-year-old Canadian hit 19 winners as she completed the victory in 59 just minutes.
Bouchard has won just one match in three tournaments since her run at the All England Club but says she is ready to step up now she is back on the grand slam stage.
She said: "They're the best tournaments of the year, they're so special. I love playing the grand slams. I want to raise my level in the big matches and on the big stages and the US Open is the biggest stage."
Petra Kvitova, who defeated Bouchard in the final of Wimbledon, had things even easier as she breezed past Kristina Mladenovic 6-1 6-0 in 52 minutes.
Former champion Svetlana Kuznetsova was eliminated in the first round of the US Open as Marina Erakovic clinched a shock 3-6 6-2 7-6 (7-3) win.
There were no such problems for Samantha Stosur - another former champion at Flushing Meadows - as she cruised to a 6-1 6-4 win over Lauren Davis.
Eighth seed Ana Ivanovic had it even easier against Alison Riske, another unseeded American. The former French Open champion broke her opponent's serve six times en route to victory.