Mackay traded in his TV microphone at the Sony Open for the 40-pound bag belonging to Justin Thomas.
It was his first time caddying since he split with Phil Mickelson six months ago. Mackay was only a temporary replacement at Waialae for Jimmy Johnson, a good friend and Thomas' regular caddie who has a nasty case of plantar fasciitis that will keep him in a walking boot for the next month.
"The toughest thing about not caddying is missing the competition, not having a dog in the fight," Mackay said before the final round. "There's nothing more rewarding as a caddie, in general terms, when you say, 'I don't like 6-iron, I like 7,' and being right. I miss that part of it."
The reward now?
"Not stumbling over my words," he said. "And being better than I was the previous week."
He has done remarkably well since he started his new job at the British Open last summer, except for that time he momentarily forgot his role. Parts of that famous caddie adage — "Show up, keep up, shut up" — apparently can apply to golf analysts on the ground.
During the early hours of the telecast, before Johnny Miller came on, Justin Leonard was in the booth.
"It's my job to report on what I see. It's not my job to ask questions," Mackay said. "I forgot that for a minute."
Leonard was part of a booth discussion on how a comfortable pairing can help players trying to win a major. That prompted Mackay to ask Leonard if he found it helpful at the 1997 British Open when he was trying to win his first major and was paired with Fred Couples in the final round at Royal Troon.
"What I didn't know is we were going to commercial in six seconds," Mackay said. "I would have no way of knowing that, but I completely hung Justin out to dry. He's now got four seconds to answer my long-winded question."
During the commercial break, the next voice Mackay heard belonged to Tommy Roy, the executive golf producer at NBC.
"Bones, don't ever do that again."
It was Roy who recognized the value experienced caddies could bring to a telecast. That's why he invited Mackay and John Wood, the caddie for Matt Kuchar, into the control room at the 2015 Houston Open so they could see how it all worked and how uncomfortable it can be to hear directions coming through an earpiece.
Both worked as on-course reporters at Sea Island that fall.
And when Mickelson and Mackay parted ways after 25 years, Roy scooped up the longtime caddie for TV.
It's common for players to move into broadcasting. Far more unusual is for a caddie to be part of the mix. Mackay loves his new job. Mostly, he loves how it has helped elevate his profession after so many years of caddies being looked upon more unfavorably than they are now.
"I want to be a caddie that's doing TV," he said. "That's what I hope to come across as. The guys think this is good for caddies. And if it's good for caddies, that makes me happy. Because I'm a caddie. I'll always be a caddie."
Not next week at Torrey Pines, where Mickelson won three times. Not a week later in Phoenix, where Mackay lives. Both events belong to CBS.
And not the Masters.
He hasn't missed since 1994, when Mickelson broke his leg skiing that winter.
"That killed me," he said, "but not nearly as much as it's going to kill me this year. I'll wake up on Thursday of the Masters and I'll be really grumpy. I'll probably avoid television at all costs until the 10th tee Sunday. And I'll watch. But it will be, within reason, the hardest day of my life."
There are too many memories, dating to when he was in the gallery right of the 11th green in 1987 when Larry Mize chipped in to beat Greg Norman. He caddied for Mize for two years, and then Scott Simpson in 1992, and Mickelson the rest of the way. He was on the bag for Lefty's three green jackets.
Mackay still doesn't talk much about what led them to part ways, except to say that a player-caddie relationship runs its course.
"If you lose that positive dynamic, there's no point in continuing," he said. "It can be gone in six months or a year or five years. In our case, it took 25 years."
He says a dozen or so players called when they split up, and the phone call most intriguing was from Roy at NBC.
"I thought I'd caddie until I dropped," Mackay said.
He never imagined getting yardages and lining up putts for anyone except the golfer whose bag he was carrying. Now it's for an audience that measures in the millions. Mackay doesn't look at it as a second career. And he won't rule out caddying again.
"It will always be tempting," he said. "I'll always consider myself a caddie. Right now, I'm very lucky and grateful to have the job I do."
Except for that first week in April.
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