Naomi Broady fights back to knock fellow Briton Laura Robson out of US Open

Robson was looking to extend an eight-match winning streak at Flushing Meadows but her compatriot Broady came from behind to seal a gutsy 6-7 (4/7) 6-3 6-4 victory.

Broady will now face either world number four Agnieszka Radwanska or American Jessica Pegula after sealing only her second ever win at a grand slam.

After a nightmare two years of injury, Robson had enjoyed an encouraging run this summer, winning an ITF tournament in Pennsylvania before coming through three rounds of qualifying.

When the 22-year-old made her breakthrough run to the fourth round here in 2012, Broady was ranked 224th in the world and had just lost in the first round of qualifying to world number 231 Yifan Xu of China.

Four years on, there has been something of a role reversal, with Broady climbing to 82nd and Robson now looking to find form and fitness after dropping to 254th.

Spectators were treated to a contest of high quality on Court 13 but Broady's consistency, and perhaps superior stamina for the intensity of competition, ultimately proved decisive.

There was very little to separate them in the opening set, a total of four points in fact, and it needed a tie-break to settle it as Broady made the early headway, pulling 3-1 clear.

Her opening point had come from a cruel net-chord, but Robson was not deterred, fighting back for 3-3, before Broady crashed a forehand down the line to move ahead again.

Robson swept a backhand into the corner to level and then bellowed with excitement when a Broady backhand drifted wide, giving her two points to serve out.

She took the first opportunity as another Broady backhand missed its mark and Robson sealed a nail-biting set in a lengthy 59 minutes.

After no breaks in the opening set, the players exchanged one each at the start of the second but it was Broady who seized the ascendancy with a more aggressive approach from the back.

She hit 18 winners in nine games, double her first-set total, and broke Robson twice more to force a decider.

The momentum was with her, but Broady took a five-minute toilet break before the start of the third, and had to save two break points as Robson fired a simple forehand wide.

Robson began to tighten up, serving six of her nine double faults in the final set, and finally the pressure became too much at 4-5.

Broady hit two brilliant winners to open up three match points and then sealed a hard-fought victory when Robson fired long.