Opportunity Knox for Rory McIlroy at Augusta 2015

An amateur more than twice his age, who has already beaten him once, could hold the key to Rory McIlroy’s bid to complete a career grand slam.

McIlroy's hard-fought victory in the British Open Championship at Royal Liverpool means he needs to win the US Masters to become just the sixth player in history to win all four majors.

The 25-year-old famously took a four-shot lead into the final round in 2011 only to collapse to a closing 80 which left him joint 15th, 10 shots behind the winner Charl Schwartzel.

The world number two's only top-10 finish in six appearances at Augusta National came earlier this year, but only after the embarrassment of losing to his non-competing marker in the third round.

Rounds of 71 and 77 meant McIlroy made the cut on the mark of four over par and, as the odd man out of the 51 players left in the field, had to play with a marker on Saturday.

Augusta member and two-time former Georgia amateur champion Jeff Knox had that enviable role and although McIlroy shot 71, Knox — who holds the course record of 61 from the members' tees — beat him by a single shot.

McIlroy had to birdie three of the last four holes to keep it that close — in match play he would have lost 4&3 — and said at the time: “Jeff is a great player. I thought he was going to be nice and three-putt the last and we would have a half, but he beat me by one.

“I don’t think I’ve ever seen anyone putt the greens as well as he does around here. I was thinking of maybe getting him to read a few of my putts out there.”

McIlroy was able to laugh it off at the time and a closing 69 gave him a share of eighth place, but he sounded more serious about seeking Knox’s help now that a career grand slam will be on the line when he returns to Augusta in April.

"I've always been comfortable from tee to green at Augusta and it's just taken me a few years to figure out the greens and figure out where you need to miss it and some different little shots that you might need that week," McIlroy said after holding off the challenge of Ryder Cup team-mate Sergio Garcia at Hoylake.

“I’ll be going into Augusta next year pretty confident.... if I can just figure out the greens a little bit more. What really helped me last year was playing with Jeff Knox in the third round. He’s the best I’ve ever seen on Augusta’s greens.

“I might have to take a couple of trips up before it starts next year and have a couple of practice rounds with him.”

With a six-shot lead after 54 holes at Royal Liverpool, McIlroy was asked what it would mean for him to lift the Claret Jug and correctly answered with a smile: “A lot of hype going into Augusta next year.”

Only Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Tiger Woods have won all four major titles in their careers, an exclusive club McIlroy now has the chance to join.

Sarazen was the slowest to win his grand slam, needing 40 events from 1922 to 1935, but he did have the excellent excuse of the Masters not even existing until 1934. Hogan needed 28 events and Player 24, with Nicklaus requiring 18 and Woods just 15.

Assuming he plays in next month's US PGA Championship at Valhalla, McIlroy's first attempt to complete the grand slam next April will come in his 25th major appearance as a professional. He was joint 42nd in the 2007 Open as an amateur.

It is all a far cry from 12 months ago when he experienced the lowest point of a largely miserable 2013 by missing the cut at Muirfield, labelling his own play “brain dead” after an opening 79.

Struggles on the course were not helped by problems off it, McIlroy admitting in November he had seen enough lawyers to last him a lifetime as a dispute with his former management company headed for the courts.

But the former world number one eventually got to grips with his new equipment and secured a first win of the year in December, while he somehow won the BMW PGA Championship at Wentworth in May despite announcing on the eve of the tournament that he had called off his wedding to tennis star Caroline Wozniacki.

“I never had doubts,” McIlroy insisted. “You can’t doubt your own ability and all I had to do was look back at some of the great tournaments that I played. The ability was still there. That wasn’t it. It was just trying to find a way to make it come out again.

“Missing the cut at Muirfield last year was a very low point. I’d never missed a cut at the Open before and I really missed playing the weekend. I said to myself I’ll try to never make that happen again.

“It’s been huge what a difference a year makes, I guess. It’s turned into a great year.

“The win at Wentworth was huge and obviously getting my third major is a huge step in the right direction. There’s many more tournaments and many more trophies that I want to win.”