Sixteen-year-old Harry Wilson made his international debut on Tuesday as a substitute against Belgium, becoming Wales’ youngest ever senior player.
His grandfather Peter Edwards, 62, was quoted odds of 2,500/1 when he placed the bet with a bookmaker in Wrexham.
He is now set to retire a year earlier than originally planned.
Wrexham-born Wilson came on in the 87th minute during Wales’ 1-1 draw.
At 16 years and 207 days, the Liverpool midfielder was 108 days younger than previous record holder Gareth Bale, now the world’s most expensive footballer following his recent move to Real Madrid.
There had been speculation that England were ready to try to persuade Wilson to switch international allegiance, but he opted for Wales.
Mr Edwards explained how he felt when Wilson made his appearance.
“I was shattered because I had to wait for 85, 86 minutes before he came on and I was panicking because they’d already substituted twice, so I thought he wasn’t going to make it,” he said.
“But when he came on I had another glass of wine. (I was) a proud granddad first for sure.
“I told my wife at half-time that my pulse was 106 – I didn’t know whether that was good or bad.”
Mr Edwards said Wilson had showed an interest in football from a young age.
“When he was about 18 months old he used to chase a ball around on the carpet before he could walk,” Mr Edwards said.
“I went into William Hill in Wrexham and asked them how I go about it. I had no idea how to do it and the manageress put me in touch with London.”
Electrical contractor Mr Edwards, of Corwen, Denbighshire, works away from home most of the year, spending one weekend a fortnight with wife Dorothy, 58.
“She is over the moon. I retired immediately. I told my manager yesterday that if Harry plays I wouldn’t be coming back,” said Mr Edwards.
“I’ve retired one year early. I have come home now and will not be going back. Not bad for a daft bet.”
He said after Harry enrolled in the Liverpool FC academy his skills quickly developed and he returned to William Hill in the hope of placing a second bet.
“Harry was about 12 then. But they turned me down and said I already had a substantial bet with them. But they threw in England as a gesture of goodwill,” he added.