Phil Mickelson and his daughter Emma watch as his son Oliver putts during the par-3 contest Wednesday. (Jim Watson/AFP/Getty Images)

When Phil Mickelson watched the seminal Masters of his youth, Jack Nicklaus’s rousing triumph in 1986, he was a 15-year-old amateur with a looping, left-handed swing and a future filled with promise. At that time, to a teenager, Nicklaus just seemed so old, a 46-year-old outlier, an established legend merely adding to the lore.

Thursday, Mickelson will tee it up in his 22nd Masters, a leading contender in what is widely considered to be a wide-open tournament. At 43, he is coming off a year in which he won his first British Open, further rounding out his résumé. He has won three times at Augusta National Golf Club — the first 10 years ago — and there is no one in the field who believes he can’t win again, himself included.

In discussing all these topics earlier this week, Mickelson turned the conversation, unsolicited, to the man whose absence helps shape the tournament, too: Tiger Woods — four times a Masters winner, out indefinitely after back surgery.

“It’s a weird feeling not having him here, isn’t it?” Mickelson asked before anyone could even bring up the question. “He’s been such a mainstay in professional golf and in the majors. It’s awkward to not have him here. I hope he gets back soon.”

But Woods’s absence, too, points to a divide that’s already developed between the careers of Woods and Mickelson, one that could shape not only this Masters but those going forward. Woods, without a major title since he was 32, is now the textbook example of how age and injuries can wear down golfers, even in their late 30s. Mickelson, with all five of his majors since he turned 33, provides the opposite model, an example of the possibility that exists for players into their 40s.

Nicklaus, to this point, is still the oldest Masters champion. But even as Woods continues to break down — this is the fifth major he has missed with injuries in the past seven years — Mickelson and others would hardly be surprised if someone closer to 50 than 40 eventually won here.

“I think everyone gets a window,” defending champion Adam Scott said. “And you might get more than one.”

Mickelson’s window opened more than 20 years ago, at age 23, when he first recorded a top-10 finish at a major, a tie for sixth at the 1993 PGA Championship. In the nine Masters from 1995-2003, he finished in the top 10 seven times and was third four times. It’s hard to remember now, but in the early 2000s, just as people counted Woods’s major titles, they ticked off Mickelson’s failures. When he arrived at Augusta for the 2004 Masters, he was 0 for 41 as a pro at majors.

“There was an amount of pressure that became relief that I won, as opposed to joy,” Mickelson said. “Now, whenever I win — when I won the British Open last year, I just felt so ecstatic and such great joy to have had that accomplishment, and there was really no sense of relief in there.”

That is because, even two decades into his career, he is comfortable both with what he has accomplished in the past and what he might accomplish in the future. Woods’s pursuit of Nicklaus’s record 18 major titles could easily be seen as a burden. Mickelson isn’t worried about any such thing. More significantly, he isn’t worried about his health. He withdrew from the Texas Open two weeks ago with a pulled muscle in his side. But it was nothing more than that, and dating back to the 1993 PGA Championship, he has missed only one major — the 2009 British Open, when his wife, Amy, was undergoing treatment for breast cancer.

Mickelson attributes this run, in large part, to his long, smooth golf swing, one he said is modeled more on that of the late Bobby Jones, one of Augusta National’s founders. He uses a wide arc to create speed through the ball, and takes a massive cut each time.

“What this has allowed me to do is play 20-plus years fairly injury-free,” he said. “. . . Because my swing is based on length and leverage and I haven’t had the injuries, I feel like I’m able to compete at a much older age or later age than a lot of the players that have such a short, violent, high-torque golf swing.”

He didn’t say it, but Woods’s swing — particularly when he was in his 20s — would fit that description. But back injuries aren’t limited to players who attack the ball. Steve Stricker, a 47-year-old once ranked third in the world, said this week he has dealt with herniated discs in both his neck and back. Even the languid Fred Couples, the 1992 Masters champ with a buttery swing, has battled back issues for the better part of two decades.

“It is an awkward motion,” said former U.S. Open champ Jim Furyk, also 43. “Guys are good athletes now and they are bigger and stronger and swinging a lot faster, and over the course of time, it takes its toll.”

So even as Mickelson pushes the outer limits of what can be achieved by a golfer in his 40s, a group of contenders here this week looks at the landscape differently. Scott and Justin Rose, the winners of the most recent Masters and U.S. Opens, have not shied away from saying this is their time.

“Twenty to 30, you can always put things down to experience, you can put things down to learning, you can chalk things up to, ‘Well, that’s going to help me in the future,’” said Rose, who like Scott is 33. “But from 30 to 40, that really is the time to do it. You don’t want to be looking too much into your late 30s, early 40s, to be trying to achieve your career goals. . . . The time is now for me. I think I am in the prime of my career.”

That is, no doubt, true. But it is also true that Mickelson could contend here this year, next year — for the foreseeable future, to the point where Nicklaus in 1986 may no longer seem an anomaly, but something approaching normal.