PACIFIC PALISADES, Calif. -- Phil Mickelson is 46 years old, playing for the fifth consecutive week, and just posted a 4-under 67 in the opening round of the Genesis Open. Tiger Woods is 41 years old, not playing once again this week, and is nowhere to be seen at a tournament he's hosting for the first time.

The parallels between golf's two biggest stars of the past quarter-century are so twisted they've become perpendiculars -- literally. While Mickelson is standing tall on the leaderboard, Woods is reportedly suffering so much back pain that he has been advised to remain horizontal.

There remains a stunning dichotomy in their divergent career paths. Once the game's most dominant player, Woods was a chiseled, steely-eyed, no-nonsense competitor, the rare golfer who could intimidate opponents simply by stepping onto the first tee. It was enough to relegate Mickelson, arguably one of the top 10 players in the game's storied history, to the role of second fiddle for much of his prime.

How did we get here? How did the years so abruptly affect one of them and so barely affect the other?

There are plenty of theories, each with varying degrees of accuracy. It can be argued that Woods' longtime strength and conditioning regimen forced his body to break down at an earlier age. It can be debated that Mickelson's less violent maneuver through the ball has allowed him to remain physically healthier.

Phil Mickelson, at 46, is playing his fifth straight tournament this week at the Genesis Open and is on the first page of the leaderboard after Round 1. Gary A. Vasquez-USA TODAY Sports

Mickelson was recently asked about the key to such longevity in his career, and pointed to two main components which have kept him competitive.

The first is the workout routine he has set up with his team of trainers.

"Our workouts are designed to be built around golf and elongating careers, so building the stabilizing muscles rather than building up just the big muscles," he explained. "The support around my knees, around my spine, around my shoulders -- all the areas that first commonly get injured -- are much stronger. Those small muscles are much stronger."

The second is his swing.

"The swing I have does not put a lot of pressure on my low back and spine," he said. "[It uses] the leverage and motion to create speed rather than a violent, brutal force while isolating a couple of joints."

Neither of these answers are in direct comparison or contrast to anything Woods has employed in the past. Mickelson wasn't saying what he does is right, just that it's right for him.

After all, there is no right or wrong answer when it comes to who went about things the "better" way. We can't maintain that Woods would give his 14 major championship titles for Mickelson's five if that meant he would still be competing pain-free on a regular basis, just as we can't say Mickelson would accept the opportunity for nine more majors but more injuries.

Woods is keen on certain buzzwords and catchphrases. Here's one he has often reminded us about in recent years: "Father Time is undefeated." His untimely departure from competitive golf -- for now, at least -- is proving that adage true, though Mickelson remains 2-up on the back nine in his own match against Father Time.

Sure, there have been setbacks. During the recent offseason, Mickelson underwent two surgeries for a sports hernia. They would've been bigger news if they hadn't occurred right around the time Woods was returning from a 16-month absence after two of his three back surgeries.

Not that they've slowed down the lefty. He began his year at the CareerBuilder Challenge and has played each of the five West Coast events since then, making the cut in the first four.

Now here Mickelson is at Riviera, in early contention for his first victory in nearly four full years, while his longtime rival is suffering through further pain.

Following his opening round on Thursday, Mickelson was asked about the disparity between the current state of his career and that of Woods.

"That's hard," he said. "It's not a fair comparison."

He then paused. At this point, we might have expected Mickelson to point out it's not fair because he never worked out as strenuously as Woods, or because his swing never placed as much pressure on his body.

Instead, he offered just a brief rationale behind his contention.

"Because I'm five years older."

Then he just smiled.