The private role Andy Murray played in the rise of Emma Raducanu

Andy Murray has called on British tennis to "capitalise" on Emma Raducanu's "incredible" success by getting more youngsters involved than the sport managed when he broke through.

The double Wimbledon champion, who has been critical of previous efforts by the Lawn Tennis Association, said there was now a "huge opportunity" as he hailed her "incredible" US Open triumph.

"It was incredible what she did there," Murray said of Raducanu taking New York by storm, not dropping a set en route to victory as she became the first qualifier in history to claim a grand slam crown.

Murray had been messaging Raducanu privately throughout her meteoric rise this summer and has mentored her for several years. Speaking after his Rennes Open first-round victory over Yannick Maden, he added: "I think for a lot of the people involved in British tennis, we knew she was extremely good. She hadn't competed much for the last sort of 18 months or so with school and coronavirus and those sorts of things, but I think at Wimbledon (where Raducanu reached the fourth round) everyone sort of got a bit of a glimpse of how good she could be."

Watch: Emma Raducanu says US Open win 'was best time of my life'

The 18-year-old's coaching staff had been seen wearing Murray's Castore sportswear range while watching her at the US Open. Her team had been wearing the kit as part of a deal the brand struck with the LTA rather than any direct connection with the two-time former Wimbledon champion. However, the pair, who had played and trained together months prior to her breakthrough Wimbledon senior debut, have become close.

"He is very fond of her and thrilled by her progress," one source close to Britain's two tennis superstars told Telegraph Sport, adding that messages had been exchanged.

Murray, speaking after his match, added: "I've spent a little bit of time around her on the practice court, but more so in the same building, training close to each other, and watching what she's doing, and she's obviously really, really good.

"But what she did in New York was very special, a huge boost for British tennis and gives hopefully the governing bodies an opportunity to capitalise on that and get more and more kids involved in the sport. It's great what she did and a huge opportunity for British tennis now."

With Raducanu's father, Ian, deciding that she should be prioritising her A-levels as her tennis career was delayed by the pandemic, she and Murray trained together during the off-season last December. Video footage on social media showed the pair rallying. The pair had also met in two mixed doubles fixtures at the Battle of the Brits at Roehampton.

Raducanu had described how the matches had particularly helped her return of service. "I played against Andy twice at the Battle of the Brits - it was great to see how fast the incoming ball is at that level in the men's game, so it was a great experience just trying to return his serve," she said last year. "He's great and the thing that makes him a great competitor is the big points - he knows exactly what to do, when to push and which points matter. He definitely zones in for the more important points, and you can feel that as it means there's pressure on you."

Raducanu has career links with Murray going back to 2019, when she and Jack Draper were announced by Amazon as winners of its Prime Video Future Talent Award in November 2019. Each scooped £30,000-a-year in funding along with "mentoring" from Murray. She has also enjoyed a practice session with him at Wimbledon.

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Murray has been relatively quiet on his social media feeds in recent weeks, but is believed to have been sending private messages congratulating the heir to his throne as the biggest star in British tennis.

Having already dwarfed Murray’s earnings at the same age, Raducanu is on the right path to overhauling his career total of $62,059,682 (£44,859,841) on the court and the tens of millions extra he has gleaned in sponsorships and endorsements off it.

Marcel Knobil, founder of Superbrands and the Brand Council consultancy, said: "Her bank manager would be very surprised and disappointed not to see £20million in the bank within two years from sponsorship alone." Steve Martin, global chief executive, M&C Saatchi Sport & Entertainment, had backed her to become bigger than Murray even prior to Saturday night's final.

The Lawn Tennis Association is hoping to generate more Government funding to refurbish crumbling public park courts. LTA chief executive Scott Lloyd says 40 per cent of park courts are "in poor or unplayable condition".

Murray, however, has previously been critical of efforts to nurture fresh talent. “Nothing ever gets done," he said in 2015. "So I don’t want to waste my time talking about stuff. I don’t speak to any of the people who are in a high-up position about that. I don’t know where the next generation are. It is a shame because, regardless of whether or not we had a load of players at the top of the professional game, the juniors were never a problem before."