The American amateur is Augusta's official 'marker', which means he makes up the numbers when the field is one short

On Saturday night millions of people around the world took to the 1st tee at Augusta for the final round of the Masters. And then they woke up. But there is a man who gets to live out the dream shared by all those hapless hackers. His name is Jefferson Knox and for the last decade he has been Augusta National's official "marker".

That means when the field is one short, as it has been after the cut this year, he makes up the numbers. On Saturday he played with the defending Masters champion, Bubba Watson, and on Sunday he was paired with the 2011 PGA champion Keegan Bradley. You might imagine that, as a 50-year-old amateur, Knox would come off poorly in that kind of company. You would not be the first to be fooled into thinking that. Given that he is representing Augusta National, it would not do.

In 2006 Knox played the final round with Sergio García. Whisper this, because the members would not look too kindly on such a tale getting around, but the two of them are reputed to have put a little something on the side, just to make things interesting.

Knox's scores do not count, after all, and García had blown up the previous day and was nine shots off the lead. "I remember seeing them all come down the fairway on the 18th. Sergio had just sent his drive way over into the trees," one long-time Masters spectator says. "And Jeff and his caddie had these big old grins on their faces." The story goes that García refused to shake Knox's hand when the round was over.

"Yeah, I played pretty good against Sergio," Knox said afterwards, with a forgivable hint of self-satisfaction. He made par, which was one better than García managed.

The Spaniard should have known better. Knox holds the course record around Augusta National – a 61 which he shot in 2002.

That was off the members' tees, which are a lot more forgiving than the ones used during Masters week. Off those Knox's best score is a mere 69.

The Knox family draw a lot of water in Augusta, and not just because of Jeff's golf game. His father, Boone, was also a club member.

He was a handy player himself, once entering the British Amateur Championship, but he spent most of his time building his business empire. It got big enough to allow him to make a $2m (£1.3m) endowment to Augusta State University in 2008 and pay for the Salvation Army centre downtown.

With that kind of legacy behind him, Knox surely has plenty of time to practice. He is reckoned to be the best amateur golfer in Augusta, though he finished runner-up to his own son, Lee, at last year's state championships.

They say Knox's win-loss record against his playing partners in the Masters is a little better than 50-50. It helps, of course, that he does not have to deal with the pressure of trying to make his way up the leaderboard. But then that has to be balanced against playing in front of a crowd of 30,000.

Jim Furyk played one round with Knox back in 2006 and said afterwards that he reckoned he could "beat half the field who made the cut".

Knox first got the call to play in 2003, when he was paired, twice, with the 1982 champion, Craig Stadler. He beat him both times. In 2006 he outdrove Miguel Ángel Jiminez on the 1st tee. Jiminez turned to him with a grin, wagged his finger and warned :"Don't you dare outdrive me!"

Knox could not help himself. He did it again at the 10th. And last year he licked the US Amateur champion, Kelly Kraft, by two strokes, 75 to 77.

Knox was at it again on Saturday, giving Watson a free lesson in how to play Amen Corner. At the 11th he played a deft approach and made two tidy putts to set up a par, while Watson dumped his second shot into the water, clumped a chip on to the edge of the green and ended up with a double bogey.

Then at the 12th, "the hardest hole in tournament golf", as Jack Nicklaus calls it, Knox knocked his tee shot to eight feet from the hole and rolled in the putt for a birdie. "That was kind of neat," he said afterwards. "In front of that huge crowd I couldn't feel my knees."

One would never know it. He has an easy air on the course, as if he is a little amused by how hard a time his partners are having. On the 5th on Sunday he stood leaning on his putter, one hand in pocket, while Bradley was trying to figure the best way out of the mess he had made for himself when he hit his second into the grandstand.

Knox, of course, had rolled his own approach right on to the fringe of the green. "No one wants to play with me very much," Knox said with a grin when his round was over, "because that means they're in last place."

That may be true but it is not theonly reason.