Open Preview: Burden of the bag-carriers: Owen Slot analyses the wide-ranging role of the master caddies

SUNDAY night at Oakmont, Pennsylvania, the eve of Ernie Els's US Open victory three weeks ago, made for a sleepless few hours for Ricky Roberts, his caddie. It was not that he was nervous about the three-way play-off the following day, more the burden that his conscience was carrying for not taking Els home to victory that afternoon. Els could have - should have - won it already, and Roberts blamed himself.

'On the 18th tee on the Sunday, I wish I'd held Ernie back. Just for 50 seconds,' he said. Ahead, on the green, Loren Roberts had just missed a putt, leaving Els requiring a par four to win. Els did not realise, though, hammered his drive in search of a birdie, hooked it and took five. 'That evening,' the caddie reflected, 'I went out to dinner with Frank Nobilo and his caddie, and I was cursing and swearing. Then I was up at 3am, stomping round the room. It was a nightmare.'

Roberts slept better the following night - Els had won - but he will not be making the same mistake in The Open at Turnberry this week. Of all the decisions a caddie has to make, knowing when to interject is one of the hardest. Some players expect assistance, others will snap at so much as a suggestion, but Roberts acknowledges that his judgement was wrong.

Caddies refer to their relationships with their players as 'marriages'. Those who make their marriages last longest are not simply the caddies who select the right club or give the correct line on a putt, but those who are masters of the mental game, who know when to massage the player's ego, when to advise, and how to cope with bursts of frustration. Bernhard Langer and Peter Coleman have been married, with just one brief split, for 13 years now, a span eclipsed perhaps only by Manuel Pinero and Jimmy Cousins. Of course, the player must be successful; at wages of pounds 250 a week plus around 7 per cent of the winnings, it takes no small amount of prize money to win a caddie's commitment to a marriage. But with the best, the rewards are large: Coleman and Fanny Sunesson, Nick Faldo's caddie, earn an estimated pounds 200,000 a year.

It is a far cry from 1951 when Willie Aitchison first caddied at The Open, when his peers would carry whisky flasks in the pockets of their long grey coats and would camp out at night. Since then, Aitchison has brought home three winners: Lee Trevino in 1971 and 1972 and Roberto DeVicenzo in 1967, the year before yardage books became available. 'I'm the last ever to eyeball an Open championship. No yardage: just my eyes and instinct. Now they just pick up a book and away they go. And a lot of them don't know how to be a good psychiatrist.'

Aitchison will be picking up his caddie/player friendship with Trevino at Turnberry this week ('He lets off steam at me and I'm his straight man') but every team has its own formula. Bobby Millen, who will be shouldering Ben Crenshaw's bag for the 20th year this week, describes his role thus: 'I try and make Ben think about the shots he should hit, that instead of the dartboard golf he's playing in the States, to chase the ball into the green. He's already thinking that way, but I just try and confirm it.' And when the going gets rough, does Millen feel it? 'No. Ben's a choirboy.'

But some are not. Ballesteros and Faldo, in their early days, were not known for giving caddies an easy ride, and Howard Clark, for whom Millen has also caddied, is the most notorious. 'Howard lets you know instantly if he's not happy. Off the course, he's one of the nicest guys; on the course, he gets very intense. If he's suffering, he'll want you to suffer too.'

The pressure on such relationships is sometimes so great they will break, as Jose Maria Olazabal discovered when Dave Renwick left him, a month after his US Masters victory in April, following a dispute over the size of Renwick's bonus. The sympathy, among his peers, went all Renwick's way ('The Spanish chaps are renowned for coming up a zero short,' Millen said) but his eight years with Olazabal will not be forgotten: he is still nicknamed 'Olazabal Dave'.

That split was way short of the explosion Neil Coles witnessed from Arthur Maidment, better known as Chingy, in a practice round at Muirfield in 1966. Told to keep up, Chingy dropped the bag on the fairway and stormed off, returning only to fire a barrage of swear words and a set of car keys at his now- former employer.

Such splits are not healthy. Most of the favourites for Turnberry next week are in long-standing and stable relationships. Perhaps the best known marriage was that of the late Alfie Fyles with Tom Watson, whom he brought home to five Open championships. The first of these was in 1975 at Carnoustie where Watson arrived too late even for a practice round. Fyles was known to say that 55 per cent of that victory was down to him and not many were prepared to argue.