Cayce Kerr (left), caddie of Fijian Vijay Singh, gestures before Singh's putt on the 2nd hole during Round 1 of the 2015 Masters Tournament at Augusta National Golf Club on Thursday in Augusta. Photo: CFP

When Vijay Singh pitched in for birdie from 44 yards at the first hole at the Masters on Thursday, his caddie deliberately refrained from showing too much excitement.

Cayce Kerr is working his 29th Masters and has been around long enough to know the importance of keeping his player on an emotional even keel.

"You know there are going to be lows (as well as highs), so what are you going to say then, 'You're terrible?'" Kerr said. "You've got to have some balance. You don't want to get too excited."

Caddies, a bit like poker players, have to successfully meld mathematics and psychology, but without being able to sit on their backsides all day.

And unlike their boss, a caddie cannot afford to let his head drop and attitude sour, no matter how bad the player is performing.

"When they're not playing good, that's when you have to do a better job," said Kerr.

"You can never have a bad day as a caddie. What's kept me in the game for so long is that I caddie as though I'm one shot away from being fired on any given day, so that makes you perform, or at least try to."

Caddies have some relatively easy tasks, like keeping their player supplied with water, "You don't want your horse to die on you," Kerr joked, but sooner or later in most every round there is a moment of truth.

A player, undecided on club selection, asks for the caddie's opinion, and the bagman cannot shy away from an answer. He must go out on a limb and, if wrong, incur the player's wrath, or in some more extreme cases termination of employment.

"You know your player is going to ask you to make a couple of calls that will put you on the line," Kerr said.

"Normally you have the answer but at Augusta because of the wind, the elements here can change rapidly. You have to pay attention."

Kerr was as upbeat as ever as he enjoyed a quick lunch in the Augusta caddie shack before meeting his boss on the range for a one-hour post-round practice session in the relentless afternoon sun.

2000 Masters champion Singh, 52, still retains the same workaholic attitude that took him from a humble upbringing in a Fiji shack to three major titles and the world No.1 ranking.

After that, Kerr was finally able to return to his rented house and ice the right ankle that he broke in January when he slipped on ice in Chicago.

He is still limping slightly, and the Masters is his first tournament back, but he would not miss it for the world.

The Californian has worked for six different players at the Masters, five of whom have won a green jacket, though not when Kerr was on the bag.

"Caddying overall is exhilarating but here it's extra special," he said.