Ironically, Hicks made this week's field as a last-minute replacement after missing out in a play-off in sectional qualifying.
With experienced bagman Anthony Knight back again alongside leading Australian Aaron Baddeley, two Mount caddies are appearing in the US Open for the second year running.
Butler headed for the United States with top New Zealand golfer Phil Tataurangi, but when injury-prone Tataurangi pulled out of tour golf he helped Butler find other caddying work.
Hicks played the USPGA Tour last year and is now back on the Nationwide Tour, while Presnell is 25th on the money list and in line to pick up his PGA Tour card.
Preparing for his first US Open, Presnell said: "I played a practice round with Martin Laird and FedEx Cup champion Bill Haas and it was nice to see how they're hitting the ball and to know with what I've got, I'm not that far off.
"I absolutely think I can do this. You've got to believe that.
"If you set a goal of just making the cut, then you'll probably just miss it and always come up short," said Presnell.
"Antman" Knight has become one of the most well-known caddies on the USPGA Tour, first joining Baddeley, a former Australian Open champion, in 2003. Baddeley is ranked 45th in the world and earned US$3.1million ($4million) on the tour last year.
Knight has been a professional tour caddy since 1989 and worked with New Zealander Frank Nobilo in Europe from 1992-97. Knight also had a stint with Sergio Garcia.