Lefty can heat up in a hurry

— -- LOUISVILLE, Ky. -- Jim "Bones" Mackay was guarding Phil Mickelson's bag near the parking space vacated by Tiger Woods, the space now missing the sign that had carried Woods' name. Mickelson's sign and name were still marking his turf at Valhalla, and the caddie built like a flagstick had no reason to be surprised about that.

Mackay wanted to tell a story about his boss of 23 years, and when Mackay wants to talk about Mickelson, you let him.

"One time we're playing in San Diego, eight holes to go and we're in 30th place," he said. "We're walking down the fairway and Phil goes, 'Oh man, I've got it.' I was like, 'What you got?' He says, 'Don't worry about it, but I've got it.'

"And he birdies seven of those last eight holes. The point is, Phil can flick a switch very quickly."

Saturday evening was turning into Saturday night, and Mickelson had just posted a 67 to get to 10-under at the PGA Championship, landing him 3 strokes back of Rory McIlroy. Yeah, who else?

But of the contenders in double figures chasing McIlroy, Bernd Wiesberger (12-under), Rickie Fowler (11-under) and Jason Day (10-under), Mickelson is the only one who has won a major. In fact, he's won five of them.

And yet that résumé isn't the chief reason why Mickelson, age 44, stands as the biggest threat to McIlroy's reign as the undisputed heavyweight champeeeen of golf. It's that switch Mackay was talking about. When Mickelson has flipped it in the past, he's been as dangerous as any player of his generation, Woods included.

Tiger just reached the peak of his powers far more often Phil reached his. Nobody will care about that truth Sunday at Valhalla, not with Woods catching the action along with millions of viewers on TV.

Mickelson is the most likely chaser to shoot 63, and McIlroy isn't the only one who knows it. This isn't the final round of the U.S. Open, a grueling test of manhood that might be a bit much for a man of Phil's age. This is the final round of a PGA on a soft and vulnerable course.

"You have to attack," Mickelson said.

And attack Lefty will.

"Does Phil still have the ability to have a great Sunday? Absolutely," said Mackay, the caddie who broke down and wept after Mickelson's miracle at Muirfield last summer.

"I know he's not too concerned about what it says on his birth certificate right now. Phil expects a lot of himself, and the age thing is irrelevant to him. I've worked for him for so long, and this isn't the first time I've seen him flick a switch."

Mackay has been on the bag for 41 of Mickelson's 42 PGA Tour victories, good for ninth all-time. He knows Phil about as much as his wife does.

"I know the way his mind works," Mackay said. "It's going to be a shootout tomorrow, and Phil's a very resilient guy. You cannot count him out."

Funny, but Mickelson all but counted himself out last weekend in Akron, Ohio. He was completely lost in the middle of the WGC-Bridgestone, frustrated over his inability to score, frustrated over his failure to produce even one top-10 finish on tour this year.

He called his game "just pathetic" and admitted it would be "out of nowhere" for him to contend at the PGA. And then Mickelson shot that 62 out of nowhere the next day, and arrived at Valhalla ready to take the fight to a physically diminished Woods in the first two rounds.

"Phil loves to play against Tiger," Mackay said as he prepared to load Mickelson's bag into his boss's SUV. "He was super fired up to be paired with him the last couple of days because they're never paired together on the regular tour.

"Phil accomplished a lot in the Tiger era, and we all know Rory is destined for incredible things. But Phil looks at it as a challenge, and he's so competitive. I tease him all the time that when he's 60 years old and playing in the Masters, he's going to think he has a chance."

Mickelson has a chance at Valhalla, a big one, to enhance his Hall of Fame legacy. A sixth major would jump him ahead of Byron Nelson and Seve Ballesteros, tie him with Lee Trevino and Nick Faldo, and leave him one behind the likes of Arnold Palmer and Gene Sarazen and Sam Snead.

Mickelson said he would definitely feel the pressure, a concession he wouldn't have made in the bad old days, pre-2004, when he was searching for that first major title. Asked what the other players near the top of the leaderboard might be feeling, the guys who have yet to win a big one, Mickelson said, "Hopefully more nervous and more pressure, a little tight around the collar. That's what I'm hoping for."

Even if those guys do start choking, Mickelson knows he'll need a ton of birdies to run down McIlroy. When someone asked him if the final round represented an opportunity to take chances, Mickelson ripped off another classic line.

"I don't really wait until Sunday to do that," he said.

Mickelson will be paired with Rickie Fowler, a fellow Butch Harmon player and a kid who's already one of Lefty's practice-round betting buds. But Mickelson will keep one eye fixed on the group behind him. The final group. McIlroy's group.

"He won the British Open and the World Golf at Akron," Mickelson said. "That's a huge disadvantage [for me] because I haven't been in the heat."

Only none of the other contenders can generate major championship heat quite like Mickelson.

"My game feels so close to clicking," he said. "And when I say clicking, shooting real low." Does Mickelson have one more magical Sunday tucked inside his bag? Hey, the man who knows him best, Bones Mackay, can tell you a story or two about that.