Jay Haas and his caddy/son Jay Haas Jr., line up a putt on No. 17.

He remembers being right here at Medinah Country Club, a college senior competing as an amateur in the U.S. Open. He played his way into contention, got paired with Jack Nicklaus in the third round, eventually tied for 18th.

Great memories, he said.

"It was a pretty neat week," Haas recalled. "I can't hardly believe that's 24 years ago, and I have an 18-year-old son caddying for me. It was a thrill then."

And it is now, but for a different reason. Back then, Haas had dreams of winning multiple titles on the PGA Tour, of winning major championships, of being an accomplished golfer.

Now, time is running out. He's 45 years old, with a successful career to cherish. He's won nine times on the PGA Tour, millions of dollars. But there have been no majors.

Haas leads the PGA Championship after two rounds, shooting a 5-under 67 on Friday to take a one-shot lead over Mike Weir and a two-shot advantage over Tiger Woods.

He knows another opportunity such as this may never present itself.

"It would mean a great deal," he said. "I've played a long time out here without a major win. And we all want to win golf tournaments and majors, especially, and I've not done that. I'm disappointed that hasn't happened. I'm not devastated by it, but we all think we can do better.

"Golfers are like that. Any championship is a thrill. And to have Jay (Jr.) out there with me would be unbelievable."

Haas has a pretty good record with his son on the bag. Jay Jr. caddied for his dad when he finished fifth at the Sprint International in 1997 and seventh at the St. Jude Classic in Memphis last year. They've only been together a few times, but the arrangement has worked well.

"I just get some good vibes with him," Haas said.

"He has a really good demeanor on the course. He's very level-headed, very low-key, doesn't get excited. And I think that rubs off on me a little bit. I have a tendency to get pumped up when I'm playing well. But nothing seems to excite him to the point of getting flustered."

Haas broke from the pack early with three birdies on the front nine, then added more at the 10th, 13th and 15th before bogeying the last hole.

He has not played particularly well this year, with just two top-10 finishes. And at this stage of his career, with 23 years under his belt, he's wondered a few times if he might never be in this position again, especially in a major.

"You just don't get that many opportunities and chances," he said. "Or you may not be playing well that week. At 45, I'm thrilled to be standing here. I don't think I'm washed up by any means. But people are probably shaking their heads a little bit.

"I'm trying not to look forward to the Senior Tour. I'm trying not to think, 'Well, even if I play poorly now, it doesn't matter because maybe in five years, I'll do OK on the Senior Tour. I can't afford to think that way. I have to think I can still compete out here. At times I can."

Bob Harig, who covers golf for the St. Petersburg Times, writes a column every Tuesday for ESPN Golf Online.