The more things change, the more they stay the same.

At least it seems that way, especially in the game of golf.

Much has changed since the summer of 2008 when Tiger Woods last won a major championship. In the 21 majors since that time (four of which he missed due to injury) 18 different men have taken home a green jacket or a trophy. Fourteen of those men were first-time major winners, and 13 enter this week’s PGA Championship with that lone major still on the resume.

Between October 31, 2010 and March 25 of this year, four different players could be called No. 1 in the world – Lee Westwood, Martin Kaymer, Luke Donald and Rory McIlroy.

That’s a lot of change.

But now, as we head into the first round of the PGA Championship at Oak Hill Country Club in Rochester, N.Y., today, the 37-year-old Woods is once again No. 1 in the world. Phil Mickelson, now 43, is No. 2.

Mickelson, the 2005 PGA champion, captured the third leg of the career grand slam by unexpectedly winning the British Open at Muirfield in July, and it’s his revitalization over the last three years makes this PGA Championship all the more interesting.’

All eyes are – and should be – on Woods as he vies for that elusive 15th major, but Mickelson had gone 15 majors without a victory between his 2006 and 2010 Masters victories, and then went another 13 before capturing the British. The fact that Mickelson is winning majors again and playing well enough to once again rise to No. 2 in the world means that the rivalry people have wanted for so long may finally come to fruition.

"We've battled and we've gone head-to-head quite a few times. Not as much as people might think," Woods said of Mickelson this week. "As I was saying last week (at the WGC-Bridgestone), I actually battled Vijay (Singh) and Ernie (Els) more times, because we played around the world and have gone at it more on a global basis. But Phil and I have certainly battled in a few majors and a few tournaments here and there."

He’s not wrong. Els has had 15 top 5 finishes and three major victories while Singh also had three major wins and seven total top 5s in the "Tiger Era," which began at the 1997 Masters.

But it’s interesting for Woods to think that, because Mickelson has 21 top 5 finishes and all five of his majors in that same time frame.

"In the last five or six years, I've had some pretty good success head-to-head and I feel like he brings out the best golf in me," Mickelson said this week of Woods.

"He's a great motivator for me. He's helped me work hard. He's helped me put forth the effort to try to compete at the highest level year-in and year-out, and I've loved competing against him. He's really brought the best out of me, especially when we've been paired together, and I hope that we are able to play together for many more years."

Woods has never had a true foil. No one could really touch him when he was in his prime, including Mickelson, and none of the recent major winners has inspired true confidence that they may rise to the occasion. McIlroy seemed destined for it by winning the 2011 U.S. Open and 2012 PGA Championship, but his game has fallen apart the last year and has admitted to feeling lost.

We wonder if the 24-year-old has the mental fortitude to compete for majors four times a year, every year. He may do so one day, but it could come long after Woods has fallen from his current perch.

Recent winners who are in their prime, like Justin Rose (33), Adam Scott (33) and Bubba Watson (34) don’t really get the blood moving if they were to somehow get involved in a Sunday showdown with Woods. No, only Mickelson can do that now.

So that leaves the two old men, at the combined age of 80, with 19 total majors, to provide the sparks in the year’s final major.

"I'm as motivated as ever to compete and to play and get the best golf out of me to hopefully play against Tiger when he's playing his best," Mickelson said. "That would ultimately be the goal; if I can play as well as I can at the same time he's doing the same, I would love that opportunity."

Major winners since Woods’ last win, the 2008 U.S. Open:

• 2008: Padraig Harrington (British Open), Harrington (PGA)
• 2009: Angel Cabrera (Masters), Lucas Glover (U.S. Open), Stewart Cink (British Open), Y.E. Yang (PGA)
• 2010: Phil Mickelson (Masters), Graeme McDowell (US. Open), Louis Oosthuizen (British Open), Martin Kaymer (PGA)
• 2011: Charl Schwartzel (Masters), Rory McIlroy (U.S. Open), Darren Clarke (British Open), Keegan Bradley (PGA)
• 2012: Bubba Watson (Masters), Webb Simpson (U.S. Open), Ernie Els (British Open), McIlroy (PGA)
• 2013: Adam Scott (Masters), Justin Rose (U.S. Open), Mickelson (British Open)