“I knew he was good, but I had no idea he was that good,” said former Tour player Chandler, who as Lee Westwood’s partner was alongside McIlroy on the first three days of last week’s Alfred Dunhill Links Championship in Scotland.

“How pleased am I with signing him now? It was just staggering to watch him close up.”

McIlroy’s cheque for £147,373 sent him flying from 264th to 106th on the Order of Merit, with the leading 115 earning cards following the Majorca Classic on October 28.

He is also riding high at eighth in the Ryder Cup race and Chandler added: “I’ve told Rory that he has just rewritten what was being mapped out for him.

“I can’t see him playing in anything that does not carry cup points.”

Sergio Garcia was 19 years and eight months when he made his debut against the Americans in Boston in 1999. McIlroy, leading amateur at The Open in July, would be four months younger if he is part of the team in Louisville next September.

“I knew at the start of the week I needed to do something pretty special to get my Tour card and I am absolutely ecstatic,” said the player himself.

“There have been a lot of great players come into the game pretty young, obviously Tiger (Woods) and Sergio (Garcia) and I’m trying to take it all in my stride. When I talked about my chances of making the card this week to Lee he told me I could win the tournament.

“When someone like Lee tells you that it gives you a lot of confidence. Hopefully this is a huge step for bigger and better things.”

Former Open champion Paul Lawrie partnered McIlroy on his professional debut three weeks ago and he commented: “There is nothing he can’t do – he is going to be a hell of a player.”

Originally turned down for a sponsor’s invitation to this week’s Madrid Open, McIlroy could now be about to receive one after Chandler spoke with Tour chief executive George O’Grady.

But with next week’s Portugal Masters, where he does have an invite, much bigger money the decision may be taken to have a week off.

Nothing, though, will give Chandler greater pleasure than withdrawing the teenager’s name from the long list of players striving to come through the Tour’s qualifying school next month.

McIlroy was down on one over par after starting his second round at St Andrews last week by going in the burn short of the green for a double-bogey six.

But Chandler said: “I thought at the time it could be the best thing for him. I felt there was a ton of birdies in him and his head did not go down for a minute.

“That was the most impressive thing – that combined with the variety of shots. He shapes the ball both ways depending on where the flag in, sometimes he puts fierce spin on it and other times he lets the ball run up.

“In that he was Tiger-esque and you just don’t hit the shot he hit into the 17th in the final round unless you can really play.”