PORTRUSH, Northern Ireland – For most, Harry Diamond is simply identified as Rory McIlroy’s caddie. Some might take it a bit deeper and point out the two were best friends growing up in Northern Ireland and that Diamond was the best man at McIlroy’s wedding.

But as McIlroy explained Wednesday at Royal Portrush, site of this week’s Open Championship, Diamond was an accomplished amateur whose experience could be particularly helpful this week.

“I think that's one of the things people don't realize, Harry has played more rounds of golf on this golf course than I have, and definitely more competitive rounds,” said McIlroy, who shot a course-record 61 as a 16-year-old in the North of Ireland Amateur held at Portrush in 2005. “He's just as comfortable on this golf course as I am. So that is a big help this week.”

Diamond was beaten in the North of Ireland finals in 2011 and won the West of Ireland Amateur the next year.

Although McIlroy has played his share of rounds on the Dunluce Links, the first coming as a 10-year-old, he admitted that he will be relying on Diamond this week on a course that’s changed quite a bit in the last 10 years, including two new holes for this year’s Open.

“With Harry's experience around here, not that I don't let him have any say any other week, but I think with his experience around here, my ear will be a little sharper to what he has to say,” McIlroy said.