An in-depth knowledge of the host course can be a huge advantage at a Major Championship and there are some guys who have that in abundance this week.
It has been well documented that home favourites Rory McIlroy, Darren Clarke and Graeme McDowell know all about Royal Portrush Golf Club - but they are not the only ones.
Here is a look at three caddies who have plenty of experience of this week's Open Championship venue.
Ricky Elliott - Brooks Koepka's caddie
Koepka's bagman Elliott, who has been with the American for six successful years which have yielded four Major Championship titles, hails from Portrush. Such is Elliott's perceived inside track that 15 time Major winner Tiger Woods texted World Number One Koepka to ask if he could play a practice round with the pair. But Koepka revealed he did not see the message, having recently changed his number. Speaking about Elliott, Koepka said: "I don’t think when he grew up that he ever thought there would be an Open Championship here and to top it off, I don’t think he ever thought he’d be a part of it. And to be caddying and to be able to win one here – he’d be a legend, wouldn’t he? He already is. But it would be cool to see him win."
Harry Diamond - Rory McIlroy's caddie
Diamond is a childhood friend of McIlroy's and a very good golfer in his own right who feels right at home on the rolling links at Portrush. Earlier in the week, Northern Irishman McIlroy said: "One of the things people don't realise is Harry has played more rounds of golf on this golf course than I have, and definitely more competitive rounds. He reached the final of the North (of Ireland Amateur Championship) a few years ago. He's just as comfortable on this golf course as I am so that is a big help this week."
Mick Donaghy - Tyrrell Hatton's caddie
Hatton's caddie Donaghy was on the bag for Jamie Donaldson when he won the Irish Open at Portrush in 2012. And with the English Ryder Cup star making a strong start to the week on the Northern Irish coast, could Donaghy be on the winning team again this week? Hatton said: "He knows where he’s going and he’s got plenty of experience."