PEBBLE BEACH, Calif. -- These relationships are really not meant to last. Inside the ropes, a golfer has only his caddie and nobody else. That person can become an easy scapegoat.
Nerves fray, tensions build. Just as a new putter, driver, agent or swing coach can shake a player out of golf's doldrums, hiring a new caddie -- thus firing the old one -- is simply business.
And some players change caddies like golf gloves.
All of which makes the relationship between Phil Mickelson and caddie Jim "Bones" Mackay all the more remarkable.
Mickelson, who will turn 40 on Wednesday, began his professional career in 1992 at the U.S. Open here at Pebble Beach Golf Links.
He had hired Mackay, now 45, just weeks prior, and they have been together ever since, with "Bones" on the bag for each of Lefty's 38 PGA Tour titles, including a fourth major championship at April's Masters.
Together, they will try for No. 5 at the 110th U.S. Open, a tournament where Mickelson has finished runner-up five times.
Throughout the years, the relationship has developed into more than player-caddie. Mickelson and Mackay are close friends, as are their wives. In fact, it was Phil and his wife, Amy, who introduced Mackay to his wife, Jennifer -- and it took some prodding.
"My wife and I knew each other for a number of years before I ever went on a date, and I was like, 'I'm not going to go there,'" Mackay said. "She was one of Amy's best friends. But they were like, 'C'mon you guys.'"
One thing you quickly learn about Mackay: He is loyal to a fault. He knows who the boss is, defends him and does not risk ruining a good thing.
It is for those reasons that Bones shies from the spotlight. He is almost as recognizable as Mickelson but prefers to stay in the background. He does occasional media interviews but doesn't want to be the story. He is reluctant to take any credit, even though it is clear that Mickelson greatly values his input, right or wrong.
Their financial arrangement is unknown, but when you consider that Mickelson has made nearly $60 million in official PGA Tour earnings alone, is known to be very generous and speaks glowingly of Mackay, you figure that Bones is doing OK for himself 18 years -- and counting -- into this gig.
"I think having Bones on the bag has been one of the most fortunate things that I've ever had, to have him in my life," Mickelson said recently. "He's a great friend as well as a great caddie.
"I had an opportunity to play some professional tournaments as an amateur and get to know him before I came out. He had written me a handwritten letter, and it was very impressive, and we gave it a try.
"He's been every bit the class act that I hoped he would be."
Mackay, who was born in England but grew up in Florida, was a decent-enough golfer to earn a scholarship to Columbus (Ga.) College, a Division II school. But he quickly learned he was not pro material. While in school, he worked at Green Island Country Club, where tour player and 1987 Masters champion Larry Mize was a member. A few years earlier, Mackay had done some caddying and "thought it was the greatest thing in the world."
That is why after being offered a full-time job in town at Synovus, a financial institution, Mackay jumped at the chance to work for Mize when the golfer said he was looking for someone, practically begging for the opportunity.
"I asked for a two-year leave of absence before I ever went to work there," Mackay said. "The man who was the longtime CEO of that bank, James Blanchard, is a member at Augusta National. Every year he asks me when I'm going to report to work."
Mackay never turned back. He started working for Mize at the 1990 Bob Hope Chrysler Classic, and it was during that season when he got pegged with the "Bones" nickname. They were at a tournament in Paris attending a group dinner that included Couples. "Back then, I was skinny. Really skinny," Mackay said. "He was trying to get my attention from across the room, and he didn't know my name. He was calling me all these names, and I was pathetically skinny, and finally he just yelled 'Bones.' For the rest of the trip that's what he called me. And it stuck."
Two years later, Mackay was a regular caddie, and he had started working for Scott Simpson, who told him from the beginning: "If you ever get offered a job by a player who is better than me, I would expect you to leave me and take it."
That chance came later in the year as Mickelson was nearing the end of his college days at Arizona State.
And it all came together in a "Did it really happen that way?" sort of scenario.
Several years earlier, Mackay had met Steve Loy while the coach was recruiting another player for the University of Arkansas. Although Mackay never played for Loy and never stayed in touch, the coach remembered him.
But at this time, Loy was Mickelson's coach at Arizona State, where Lefty had won three individual NCAA titles and helped the Sun Devils to a team championship. Mickelson had won the Tucson Open as an amateur, and it was pretty clear that he had a bright future. Loy, who is now Mickelson's agent, was sizing up potential caddies for when Lefty turned pro.
He wasn't necessarily zeroing in on Mackay, just exploring all angles. Mackay wrote a letter expressing interest in the job, and there was some casual conversation about it that spring when Bones was caddying for Simpson at the Players Championship, where Mickelson was teeing it up as an amateur. Soon after, Mickelson offered him the job.
"The first time I ever caddied for him was at U.S. Open qualifying in Memphis, and he was an amateur," Mackay said. "I didn't really know him at all. We had a couple of five-minute conversations over the phone. And we didn't play a practice round. He had just won the NCAAs. He flew in and said, 'I'll see you on the tee.' And off we went.
"There were something like 80 guys for 16 spots. He shot 69 in the first round and broke the course record the second round. It was an amazing day for me.
"First, I couldn't believe how hard it was for me to clean a left-handed club. But it was incredible how talented he was. He shot 62, and then it was off to Pebble."
Mickelson missed the cut in his first pro tournament, but Mackay knew he was working for a potentially special player.
"It was such a fascinating job to have because he played so differently," Mackay said. "At that point, I had worked for Larry Mize and Scott Simpson and a little bit for Curtis Strange and a couple of other players.
"All of a sudden I'm working for this guy who hits the ball much further than any of the other guys I had ever worked for. A guy who is, 'I can pull off this shot. I can do this.' It was incredible; he's hitting it over trees, I'm looking under, he's looking over. So for me, I had to really adjust. This is the way he plays. I enjoyed it."
But Bones wasn't just along for the ride. He was determined to bring a level of professionalism and dedication to the job. Some of that came from looking up to Edwards, but he also understood the value of the opportunity and wanted to do all he could to keep it.
One example stands out. In 1993, Mackay traveled on his own to the Ryder Cup at The Belfry in England. "Phil won the International about two weeks before the Ryder Cup [but had not qualified for the team]," Mackay said. "I had a little bit of money in the bank. My best friend, Joe LaCava, was caddying for Fred Couples, and I just wanted to go and watch."
Mackay slept on the floor of LaCava's room and became something of a caddie gofer for the week, soaking it all in during the U.S. victory.
"Jim figured Phil was going to be playing in a lot of Ryder Cups," LaCava said. "He was preparing."
Good thing. Mickelson has played on every U.S. Ryder Cup and Presidents Cup team since 1994, 16 straight years of international competition during which Bones has been there for every tournament.
Mackay has experienced the highs and lows right along with Mickelson, of course. Winning his first Masters in 2004 was a huge highlight. So was this year's victory at Augusta National, where Amy Mickelson -- who just more than a year ago was diagnosed with breast cancer -- made a surprising and emotional appearance behind the 18th green, accompanied by Jennifer Mackay.
There have been low moments, too.
"Sure, there are tournaments that didn't work out," Mackay said. "For me personally, the hardest one by far was losing to David Toms [at the 2001 PGA Championship] in Atlanta. Phil played so well that week.
"But I don't know if you can call having a chance to win a major a low point. At that time Phil hadn't won a major, and you just want it so bad for him. That stung. But it was awesome to be out there with a chance. I don't want to say it's a low point. It was the most difficult."
There have been mistakes, too. Mackay still laments what he believes was a poor read he made on the 71st hole of the 1999 U.S. Open at Pinehurst, where Mickelson finished a shot behind eventual winner Payne Stewart.
"We went to 17 tied, Payne hit a 6-iron to 5 or 6 feet, and Phil hit a 7-iron to 10 feet. He asked me for a read, and I misread [the putt]. That's something that still bugs me. I think we both thought straight, and it broke right. If I could have a do-over in my career, that would no question be it."
The U.S. Open is the glaring hole in Mickelson's résumé. He has been runner-up a record five times, including last year at Bethpage and in 2006 at Winged Foot, where Mickelson famously double-bogeyed the final hole to miss a playoff.
Both have been looking forward to Pebble Beach. It is a venue Mickelson loves, where he has won the AT&T Pebble Beach National Pro-Am three times.
"The reality is he has a great track record at the U.S. Open," Mackay said. "At some of these courses, he tends to play well there. Combine that, he's played well at the U.S. Open, it's Pebble, a course he loves. And you know what? He's the 2010 Masters champion.
"There is something really enjoyable about teeing it up at tournaments being introduced as that. It's an extra kick in the pants. This entire year, you have that much more of a spring in your step because of it. As far as I'm concerned, there's nothing better."
To get that third green jacket, Mickelson executed a memorable shot at the par-5 13th hole on Sunday at Augusta National, a 6-iron from pine straw between two trees that Mackay sheepishly admits he tried to talk his boss out of playing.
There was plenty of risk, given the lie and Rae's Creek that fronted the green. Mackay, the voice of reason, also knew that Mickelson had a 2-shot lead, that he's one of the game's premier wedge players and that a birdie was still possible if he were to lay up.
Mickelson was having none of it, then laced the iron shot to 4 feet.
Certainly there will be disagreements. Or decisions that don't turn out, especially throughout 18 years of tournament play and thousands of shots.
But Mickelson, Mackay said, has never held any of the wrong calls against him.
"He's awesome that way," Mackay said. "Part of the reason he's been so successful is because he's interested to hear at times what I think, but he ultimately wants to be the one making the decision. It's a great environment to work in."
And all these years later, there have been fewer than a handful of times when Mackay did not caddie for Mickelson. Caddies are hired to be fired, but not in this relationship.
"It's not really my thing to switch around," Mickelson said. "I think that he understands my game. I understand him. We have a great interaction there.
"Again, he's a lot more than a caddie to me."
Bob Harig covers golf for ESPN.com. He can be reached at BobHarig@gmail.com.