Dan Evans is finally starting to fulfil his potential after devoting himself to tennis, Greg Rusedski told Sky Sports.
The British qualifier stunned eleventh seed Kei Nishikori 6-4, 6-4, 6-2 in the first round of the US Open on Monday to seal the biggest win of his career.
And Rusedski says the 23-year-old from Birmingham, who was ranked 179 in the world heading into the Flushing Meadows event, is finally delivering after focusing fully on the sport.
"That was an absolutely brilliant performance from Dan Evans," said the former US Open finalist, who had promised to buy Evans and his team dinner if he progressed.
"He was down a break in the first set, came back to win it 6-4, was down a break early in the second set and found a way to win that set and then really finished it off in style.
"He's finally starting to fulfil his potential. We've seen glimpses of it - he reached the third round at Queen's where he lost to Juan Martin Del Potro then he played really well this summer getting to the finals of two Challengers - and he looks like at the moment he's putting things together mentally, physically and doing all the right things.
"It's part of a lifestyle choice, though - making sure you're not going out doing things you shouldn't be doing.
"Leon Smith, the LTA's Head of Men's Tennis, has put a lot of time in and so has his physical trainer. But it comes down to the player making a choice and saying 'I want to do something with my career and look back and say I gave it my most'. That's a maturation process that is finally happening with him."
Next up for Evans will be world number 52 Bernard Tomic of Australia - but Rusedski sees no reason why the Brit can't cause another upset and says, if he maintains his dedication, he too can rise through the rankings and approach the top 50 within the next months.
"Considering he's just beaten the 11th-ranked seed here in straight sets, he's got to have some confidence and Tomic, as we know from last year when he tanked against Andy Roddick, anything can happen with him.
"This surface is playing very quick, too, and Dan likes a quick court with fast balls, so it's another good opportunity for him.
"If he carries on like this there's no reason he shouldn't get in the top 100, top 50 and then we'll see.
"But he's only done it for two or three months, it's about doing it for 365 days a year. If he commits to that there's no reason why he shouldn't be between 50 and 100 by this time next year or even sooner than that."
There was more success for British tennis in the women's draw, with Laura Robson producing an accomplished performance against Lourdes Dominguez Lino to win 7-5, 6-0.
Robson, who is the first British woman since Jo Durie to be seeded at the US Open, overcame a wrist problem to set up a second round clash with 19-year-old French hope Caroline Garcia and Annabel Croft reckons the left-hander has every chance of winning that contest as well.
"Laura's tennis was fantastic by the end of the match," said the former British number one.
"It was a very, very tricky match at the start against someone she hadn't beaten before and someone who was throwing lots at her but by the end of the match her level was almost what we saw from her when she reached the fourth round last year.
"Robson is seeded to come through the next match against Garcia, who is ranked 75 in the world. She's a talented player who is getting a lot of attention in her country, like Laura gets in Britain, and really pushed Maria Sharapova at the French Open a couple of years ago when she went a set and 4-1 up but was unable to win.
"But Laura is a little more experienced on the world stage so I'd have to pick her to go through that one."