Our man in New York reflects on Andy Murray's hard-fought win and looks at Laura Robson's hopes of another upset.
Laborsome on Labour weekend, Andy Murray stuttered his way through to the fourth round of the US Open with a display of much grit but little conviction.
Three tie-breaks were needed for the British number one to secure victory by the slenderest of margins, dropping his first set of the tournament in the process.
While Murray struggled against world number 31 Feliciano Lopez, the man expected to stand tallest on his route to a first Grand Slam, Roger Federer, floated through with finesse, facing a solitary break point in his victory over Fernando Verdasco, who is ranked five places higher than his compatriot Lopez.
Composure in the tie-breaks was the key, with Murray offering his opponent little in the way of unforced errors and reaping the rewards as Lopez buckled on all three set points.
Murray's followers are, of course, hardened to such drama-littered early tournament battles, and plenty will suggest coming through such a tight contest in such difficult conditions will serve him well down the road.
While suggestions that the Olympic win can serve as a mental breakthrough, the Scot had his usual physical preparations disrupted by the Games.
The elongated grass season prevented him taking his usual three-week heat-adjustment training camp in Miami, and the consequences were clear for all to see as he looked energy-sapped in the latter stages of Saturday's clash.
Perfect preperation
Murray is hopeful that this near four-hour battle with Lopez in temperatures above 30 degrees Celsius will serve as some sort of a substitute, essential if he does end up coming through next weekend's 'Super Saturday' to play the final with only a day's rest.
He said after his match: "Having played a match like today in the heat and the humidity, while I'm sure tomorrow I'll be tired, it may help me for the remainder of the event."
Facing a strong server like Lopez on the Louis Armstrong Stadium's quicker surface is also likely to be an ideal preparation for his fourth-round opponent, the big-serving Canadian Milos Raonic.
A straight-sets victory is difficult to see given the way the 21-year-old is holding his serve, with tie-breaks likely to play a key part once again.
Murray's patience and concentration will need to improve, having gifted both his first-round opponent Alex Bogomolov Jr. and Lopez sloppy breaks on various occassions - such lapses might be irreversible against a man who has averaged 89 per on his first serve, which has regularly cleared the 140 mph mark and produced an average of 30 aces per match.
The world number four will, however, be abundantly aware of the weapons which the Canadian possesses having lost in their only meeting this year on the clay in Barcelona.
Major upsets
While Murray remains Britain's biggest hope at Flushing Meadows, his run will once again take a backseat to Laura Robson's remarkable run on Sunday.
The 18-year-old is looking to take her third-successive major scalp when she faces reigning champion Samantha Stosur.
With faith in the teenager growing at a rapid rate, there is now a genuine confidence that she can beat a third Grand Slam champion, certainly within the Sky Sports punditry team.
Sky Bet are also display an increasing degree of respect, having made her 7/1 to beat Kim Clijsters and 9/2 to oust Li Na, they now make her a
9/4 chance to win on Sunday, while also cutting her outright price from 1000/1 pre-tournament to
40/1.
Robson's lefty forehand will give Stosur's questionable backhand a serious examination, while the Aussie's real weakness appears to be her inability to perform under the weight of expectation.
The world number nine boasts a woeful record in her home Slam, with the fourth round her deepest run and a first-round exit this year, while she has failed to land a single title since she was crowned champion here last year.
It would, however, be all-too disrespectful not to recognise the threats which the 28-year-old offers, with one of the best kick-serves in the game likely to make it harder for Robson to attack on return as comfortably as she has done.
Stosur also boasts one of the top forehands in the women's game, with an abundance of top-spin and variety enabling her to manoeuvre opponents around the court - something that will really test Robson's movement.
However, Robson does on Sunday she has already propelled herself onto the international tennis stage and created the story of the tournament so far.
