The second major of the year gets under way on Thursday, with the PGA Championship returning to Valhalla Golf Club for the fourth time, and the first since 2014.

That previous staging of the event in Louisville brought Rory McIlroy his fourth and most recent major title. The Northern Irishman enters this year's tournament in excellent form and among the favourites, but he will face plenty of competition.

Brooks Koepka lifted the hulking trophy for a third time last year and is again tipped to be in contention, headlining a list of 16 LIV Golf entrants as the fracture that has split the sport shows little sign of healing.     

However, the question on most people's lips ahead of tee-off is; who – if anyone – can stop Scottie Scheffler? The Masters champion and world number one has been out of action for three weeks following the birth of his first child, but few expect any rustiness from a man who has enjoyed a magical start to 2024.

Ahead of the 106th edition of the PGA Championship, we run through the key storylines and delve into the best Opta facts around the key contenders.

The course

The PGA Championship's lack of a permanent home may deny it the lustre of the Masters, but a return to Valhalla – a course which holds fond memories for some of golf's biggest names – should add something special.

Valhalla's fourth PGA Championship will make it the most common home of the tournament since the start of the 1990s, with only Southern Hills hosting more often since the competition was founded in 1916 (five times).

The previous three editions at Valhalla have provided plenty of drama, with the first two – in 1996 and 2000 – being decided by a playoff. Mark Brooks overcame Kenny Perry in 1996, then Tiger Woods saw off Bob May four years later for the third leg of the memorable 'Tiger Slam'.

In 2014, meanwhile, McIlroy beat Phil Mickelson by one stroke in a dramatic finish on a chaotic, stormy Sunday. In near darkness, officials moved Mickelson and playing partner Rickie Fowler off to the side to allow McIlroy to tee off on the 18th and avoid having to sleep on his slender lead.

McIlroy has failed to win on any of his subsequent 35 major appearances, but as he returns to the scene of his most dramatic success, it's no wonder the world number two feels "the stars are aligning" for him.

The contenders 

Indeed, McIlroy approaches the tournament in fine form, winning on his last two starts on the PGA Tour after enduring a mixed beginning to 2024.

Having triumphed at the Zurich Classic of New Orleans alongside Shane Lowry, McIlroy hauled in Xander Schauffele to win the Wells Fargo Championship for a record-extending fourth time last week, issuing a timely reminder of his brilliance by carding a six-under 65 in the final round.

Back in 2014, McIlroy entered the PGA Championship as the favourite after winning The Open, but he believes he is in better shape now than he was a decade ago.

"I've been banging this drum for the last few years, but I'm a way better player now than I was back then," he told Sky Sports after his Wells Fargo win.

"I haven't had the major record to back that up, but I've had the wins, I've done everything else there is to do in the game since 2014. The only thing I need to do is get another major."

While hopes are high regarding McIlroy's chances of a title tilt, he is not the clear favourite. That honour goes to Scheffler.

After his four-stroke victory at the Masters, Scheffler could become just the third golfer this century to win the first two majors in a calendar year, after Woods (in 2002) and Jordan Spieth (2015). 

He has been in sublime form this year, shooting a staggering 161 under par across 39 rounds in 10 PGA Tour events, not finishing a single round over par.

Scheffler has won on four of his last five starts, triumphing at the Arnold Palmer Invitational, Players' Championship and RBC Heritage as well as the Masters, and finished second at the other, one shot behind Stephen Jager at the Houston Open.

The 27-year-old has taken three weeks off since Augusta, with wife Meredith giving birth to son Bennett last week. Scheffler does not believe becoming a father has had a negative impact on his preparations, though.

"I talk a lot about how it's all about my prep work. I want to be as prepared as possible going into an event and, standing here today, I feel like I am extremely prepared and I feel like my game is in a good spot," he told the Golf Channel.

Should a lack of sleep get to the new dad, Scheffler can expect competition from the man who beat him and Viktor Hovland by two shots at last year's PGA Championship – Koepka.

Only Walter Hagen, Jack Nicklaus (five each) and Woods (four) have bettered his three wins at the event. 

Having gone back-to-back at the PGA Championship in 2018 and 2019, Koepka could become just the second player to win successive editions of the tournament twice in the stroke-play era, after Woods did so in 1999 and 2000, and again in 2006 and 2007.

What of 15-time major champion Woods? He has a lifetime exemption for the PGA Championship but has not played competitively since the Masters. At Augusta, he made a record 24th consecutive cut but finished last of all players to go the distance, a 10-over 82 in the third round being his worst-ever score at the event.

A Woods triumph would make even his incredible 2019 Masters comeback look like a minor upset, but he did not play his chances down at Tuesday’s press conference.

"I still feel that I can win golf tournaments," Woods said. "I just need to do it for all four days, not like I did at Augusta for only two." 

There are others going under the radar who are more likely to be in contention, though.

Jon Rahm entered last year's PGA Championship as world number one and hot favourite, only to finish with a share of 50th place at seven over for the tournament. 

Having joined LIV Golf in December before enduring a poor Masters defence, Rahm is not being spoken about in quite the same terms this time around. 

The Spaniard has, however, made the cut at each of his last 18 majors, the longest ongoing run among male golfers. The last time he failed to see the weekend was at the 2019 PGA Championship.

Schauffele and Max Homa have both been tipped for serious tilts at what would be a maiden major title for either player. 

Schauffele's 12 top-10 major finishes since 2017 are more than any other player without a title to their name, while Homa has been steadily improving, finishing T10 at The Open last year, then T3 at the Masters, having never previously managed a top-10 finish in 16 major appearances. 

The history 

The PGA Championship has not been all that welcoming to those travelling from overseas in recent years. In fact, the last eight editions have all been won by an American, the longest run of champions of a single nationality at any major since US-born players won 12 straight US Opens between 1982 and 1993.

The last non-US player to win the PGA was Jason Day in 2015, while the last European to lift the Wannamaker trophy was McIlroy one year earlier.

The likes of Justin Thomas (twice), Mickelson, Collin Morikawa and Jimmy Walker have helped Koepka establish home dominance in the last eight years. Prior to Walker's 2016 triumph, non-Americans had won six of the previous eight editions. 

Another American, Spieth, is eyeing a piece of history as he looks to complete the career Grand Slam, a feat only previously achieved by Gene Sarazen, Ben Hogan, Gary Player, Nicklaus and Woods. 

He has not made the top 25 at any major since 2019, though that T3 finish did come at the PGA.

Largely good conditions are expected in Louisville, making it highly unlikely this year's tournament becomes the first in 48 years to produce an over-par winning score. The last time the PGA was won with either an even or over-par score was in 1976, with Dave Stockton coming out on top at +1.

With 16 former PGA Championship victors taking their places among the strongest field in professional golf, expect a far higher bar to be set this time around.