When the greatest team golf competition in the world tees off on Scottish soil six days from now, there will be only one Scot playing as Team Europe bids to retain the trophy they last won two years ago in Medinah, Illinois.

While Stephen Gallacher will be the focus of most native spectators' attentions at Gleneagles - and rightly so, having more than earned the wild card team captain Paul McGinley bestowed upon him - three other Scots will be involved. Vice-captain Sam Torrance and caddies Craig Connolly and Mick Donaghy will also be doing their damnedest to ensure a home win.

Connolly will be there in his capacity as caddie to the current US Open champion, Team Europe's Martin Kaymer. The son of a bar manager, Connelly is living proof that being an errant teenager is the way to go, having once skipped off high school to caddie on the hush-hush. By the age of 16, he was earning £100 a round carrying the bags of businessmen at Loch Lomond Golf Club and feeling as rich as a king. These days, as caddie to the German ranked No.12 in the world, Connelly can accrue a lucrative income as long as he is prepared to sweat for it.

We meet at Dalmuir, the hilly, tree-lined, surprisingly beautiful park near Clydebank, where Connelly fell in love with the game in the 1980s and 1990s. If Connelly could have seen then what he has now, he would have been beside himself. "I have been incredibly lucky," he says. "Back then this door called 'caddying' opened for me and I walked through it. It is just about the only working experience I have known in my life - carrying golf clubs - and it has been amazing."

Today more than one young Scot will see Connelly whispering in Kaymer's ear on TV at a Masters or an Open and wonder how he or she might get a piece of the action when they grow up, so a brief synopsis of how it all started for him is instructive. "I played football as a kid but as soon as I discovered golf I fell in love with it," he says. "My first year at secondary school, I borrowed some clubs and came down here and played at Dalmuir. That was in 1989 and I was hooked on the game."

Whittling his handicap down to four, Connolly harboured ambitions of turning professional but acknowledged the harsh truth there were players superior to him. Then, as is often the case, lady luck crossed his path. "There was a caddie called Jack Jolly, a member of my club, who caddied at Loch Lomond," Connolly says. "They needed more caddies there, so Jack came to our club and rounded up a few of us. I started doing that round about 1993, maybe 1994, and was picking up 100 quid here and 200 quid there. I was still at school in Clydebank and thinking, 'Wow, this is great.'

"My first time out at Loch Lomond, Clint Eastwood walks on to the first tee and I'm caddying for him. I was dodging school at the time but the next morning there was a picture of Clint - with me - in the paper. I went straight home and told my dad, who was a huge Clint Eastwood fan. And I got rumbled for it at school."

Connelly's reputation as a thoughtful caddie grew and grew, first in Glasgow, then nationally, then across the United Kingdom and Europe, until he finally hit America. "From Loch Lomond I heard that Myra McKinlay, the Scottish golfer, needed a caddie at the Welsh Ladies Open, so I went," says Connolly. "Then a Dutch golfer called Mette Hageman offered to drive me from a tournament in Denmark to one in Austria on the proviso: 'I'll give you a lift if you caddie for me.' I was 18 at this point in 1996. Back then I was earning no money. There was next to no money for a caddie on the Ladies European Tour.

"Then I got the chance to caddie for Lora Fairclough, a former tournament winner, which was a step up for me, and then in 1998 I went to the States to work for the Australian player Corinne Dibnah and for Alison Nicholas, the former US Open champion. Alison's career was on a downturn by then, but I learned a lot from her. She was very professional and asked a lot of her caddie. Looking back, I can see I was on my way."

In 2002, the then 24-year-old Connelly was working on the Ladies PGA Tour in America, picking up big cheques some weeks. Something about his manner made him an appealing caddie and he was widely courted. Little did he know lady luck was lurking again just around the corner. "I started working with a girl called Rachel Teske [born Rachel Hetherington, she changed her name through marriage to Teske, then reverted to Hetherington after her divorce]. I was in Australia with her. She got a couple of top 10s, she had been a tournament winner and she said to me, 'Do you want to continue?' I said, 'I'd love to.'

"That year, at Moon Valley in Phoenix, Arizona, we won a play-off against Anikka Sorenstam to win a tournament that won Rachel $150,000 and me $15,000 as caddie. It was my first tournament win and I was thinking, 'This is great'. That was my journey from 1996 through to 2003. Rachel and I had a great year and won a couple of times. Then from 2003 to 2004 I worked with (Swedish golfer) Helen Alfredsson. Then everything changed completely in the summer of 2004."

It was in the Hebrides, of all places, that Connelly met the fate that would propel him to the top of world golf. "Hugh Marr, a friend, got friendly with [Ryder Cup player] Paul Casey. Hugh was having his stag do on Islay that summer and invited me over. Paul was there and was about to play in the Ryder Cup a few months later, and asked me if I would go and caddie for him at the BMW International in Munich. I thought, 'I've got the week off. Why not?' I went over to Germany and caddied for Paul and we finished third. It consolidated his spot in Europe's Ryder Cup team that year.

"A few weeks later, out of the blue, I got a text saying: 'Get your fat little ass out to Detroit … we need you to caddie at the Ryder Cup.' To cut a long story short, I became Paul's caddie. Suddenly, I was to caddie in the Ryder Cup of 2004. That was five Ryder Cups ago. I am about to do my sixth."

Connelly is in his second stint as caddie to Kaymer, having first answered the call of the Dusseldorf golfer in May 2010 before being let go 12 months later. Even more gallingly, Kaymer rose to become the world No 1 during that period, but such turbulence is nothing new to Connolly. Three times he has been on Casey's bag and three times they have divorced. I get the impression Connolly does not discount a fourth tour with Casey somewhere down the line.

"It can get pretty intense, [the relationship between] you and your player," he says. "You spend so much time together - on the practice range, hours on the course, maybe dining together. When the pressure is on, and things are not going well, it is then that the caddie [being fired] is an easy way out for them. Maybe, no matter what you do or say, you can no longer help them.

"Quite often a player feels a change is as good as a rest. I always say to whoever I've worked for, 'You will always find another caddie.' In a way, the player has got to be selfish - he is the most important person in that environment. The player has got to feel right. So if the caddie is deemed to be detrimental to a player's progress, he goes."

When Kaymer, then the world No.1, axed Connolly despite winning four tournaments in six months and rising to the pinnacle of golf, the German still described him as a great caddie. The two were reunited 14 months later in August 2012. "Martin will tell you himself he didn't handle at all well being the world No.1," says Connelly. "There is no handbook for that. He said himself he wasn't prepared for it - and neither was I. It was an amazing feeling for me to caddie for a major champion and the world's No.1, but the pressures that come with it are enormous."

Yes, and the money is good as well. In America alone, Kaymer has earned about $5.6 million in tournament prize money since 2012. On the basis of the caddie's traditional 10 per cent - or, if you are being cautious, 7 per cent - that is a healthy dollop for the bagman. I put it to Connelly he is one of Scotland's most successful "sportsmen".

"Maybe," he says. "I'm not really money-minded, but I guess that's easy to say when you know how much money you can make. It's not always the case, though, that if a player makes £1m, then the caddie has earned £100,000. I don't sit back and think about money. I think about how privileged I have been to work for the players I have worked for, and about the tournaments we have won. When I started out I earned next to nothing, and usually needed a bank loan to get me through the early season until some sort of cheque arrived. Back then there would be four of us [caddies] sharing a hotel room because it was $100 a night."

How does he feel about the unpredictable hiring and firing that goes with the territory? "Caddying is great fun when your player is winning," he says, "but you have got to be professional at all times. You are in golf to be in contention on the Sunday, and nothing beats that feeling. But if you put pressure on yourself, you will make mistakes. So you go through the same procedure every time - count your steps, count your yardages, make sure you say the right thing at the right time.

"On any hole you are constantly thinking, 'Where don't we want to be here?' but you don't say that to the player, because it is a negative. So you say, 'Whatever we do here, keep it under the hole … if you are in between clubs, take the lesser club, hit it a little harder, stay under the hole.'

"You have also got to be able to take criticism from your boss. You have got to be able to dust it off. A golfer will say something to you in the heat of the moment that they don't mean. If it was said in your workplace, someone would say, 'Whoa, you can't say that.' But a golf course is totally different from any other job. You have got to take criticism. A golfer will shout you out on something. You take it, you move on."

This week the circus moves on to Gleneagles for one of the greatest shows in golf. Captain Tom Watson and his Team USA had best beware of the natives - those swinging the clubs and those carrying them. n

The Ryder Cup takes place at Gleneagles, September 26-28. Visit rydercup2014.com.