When Rory McIlroy won his fourth major championship, the idea that he'd go four years without another would've been hard to accept. Yet here we are, approaching if not quite yet at the anniversary of his 2014 PGA Championship win, the grand slam still incomplete after a disappointing Sunday at Augusta and no further majors of any description added to his collection.

For some analysts, that represents underachievement and I suspect McIlroy would say as much himself. Yet there can be little doubt that among the many factors explaining his (relatively speaking) barren run, a significant one is the strength of the opposition, and that fact is underlined by the market for the Wells Fargo Championship at Quail Hollow.

Three years ago, McIlroy went off a well-backed 100/30 favourite for this event, the one he'd won to the sound of Jim Nantz's "welcome to the big-time" back in 2010, and he romped home by seven. He's won here from the front and from behind, both times in mesmeric fashion, and George Cobb's classical model is clearly one of the top-level golf courses most suited to Rory's game. Were it not for an inspired Rickie Fowler in 2012, he might've won this title three times.

Now, though, McIlroy is an 8/1 shot, and that's because Fowler, Justin Thomas, Hideki Matsuyama, Patrick Reed and many more should ensure that he'll be made to work much harder if he is to succeed. Two of them, Thomas and Matsuyama, were part of a thrilling finish to the PGA Championship here in August before the brilliant Reed held off a takingly composed charge from Fowler on the final day of the Masters.

Nonetheless, McIlroy is by some distance the most tempting of the market leaders. His failure to ask a more serious question of Reed in the Masters will have hurt, but ultimately he arrives at one of his favourite stops with stroke play form figures of 1-5, and having shown that Tom Fazio's reworking of Quail Hollow hasn't undermined his affection for it, given that he was fourth post-redesign in 2016 and a solid enough 22nd when playing injured in the PGA.

McIlroy is the recommendation for those looking for a rock-solid option from the top of the market, but it should be noted that his victory here in 2015 came after the PLAYERS Championship owing to a schedule tweak. I would've much preferred him to have shaken off the post-Augusta rust somewhere and when the Wells Fargo has sat one week before the so-called fifth major, results have been a little harder to predict. For that reason, each-way options are preferred.

Rory McIlroy is favourite to win a third USPGA

Rory McIlroy is a worthy favourite at Quail Hollow

Chesson Hadley didn't quite manage to qualify for the Masters but his form either side of it is strong, with three solo top-20s prior to last week's solid effort alongside Brice Garnett in the Zurich Classic of New Orleans, and he looks the best bet.

It's been an excellent return to the top level for Hadley, who won the Puerto Rico Open as a rookie in 2014 only to suffer a complete loss of form, falling from inside the world's top 100 to outside the top 500 before a drop back down to the Web.com Tour saw him enjoy a two-win season in 2017.

Hadley had once looked like a big talent in the making and there's mounting evidence that he's firmly back on track, having started the season with three top-five finishes, added another in Phoenix and then faded to seventh in the RBC Heritage a couple of starts ago.

His last three efforts are particularly encouraging as they provide a timely return to form, because Hadley will have earmarked this event for a long time ago given that he was born and raised in North Carolina, just a couple of hours east of this week's venue.

Playing close to home can usually be considered a positive and in Hadley's case, we don't have to guess - his first Web.com Tour win came in his hometown of Raleigh, while his form here at Quail Hollow reads a quietly progressive MC-20-11.

The latter result came after Fazio's tweaks and therefore confirms that the 30-year-old can score here and I like the fact that he plays tough courses well, albeit this should prove a good deal easier than the PGA Championship with the greens in particular expected to be slower and more receptive.

That will suit Hadley, who is sixth on the PGA Tour for strokes-gained approach this season, and it was his long game which powered that 11th place behind James Hahn here two years ago. Back playing his own ball having been let down a little by Garnett after the pair had hit the front on Sunday, he looks a big each-way player.

Speaking of Hahn, like Hadley he's a winner of the Rex Hospital Open in Raleigh so his victory here in 2016 may point towards the value of form in that Web.com event. As well as helping justify the headline selection, it suggests that Trey Mullinax could be worth a bet at three-figure prices.

Mullinax won in Raleigh the same year that Hahn won here, his first professional success, and this huge-hitting youngster has finally started to translate his form to the highest level with two solid efforts preceding a runner-up finish in the Valero Texas Open two weeks ago.

While he'll have been seriously disappointed with his efforts at the 71st hole, where he effectively handed the title to Andrew Landry, Mullinax should recognise that it was a career-best performance which confirms that he has what it takes to harness his awesome power and win on the PGA Tour.

To that end, having the distraction of a light-hearted team event last week might just have helped speed up the recovery and if he tees off here in the form he was in over the weekend in Texas, big things could await.

Quail Hollow is a long golf course, more so now that par has been reduced from 72 to 71, and I would expect this week's leaderboard to be made up of those who drive the ball well. Typically these days, that means bombing it and while Kevin Kisner and Francesco Molinari are among those to demonstrate that there is another path to success here, ultimately it's a venue suited to those who would call driver a weapon.

That's definitely the case with Mullinax, who leads the PGA Tour in driving distance, and the fact that three of the last four Quail Hollow winners led the field in distance for the week rather underlines that he's coming to a golf course which puts him at an even greater advantage.

Arriving as he does in the form of his life, there's no reason he can't do what Thomas did in 2015 and contend here as a youngster despite the likelihood that there are a clutch of world-class players towards the top of the leaderboard.

Sticking with the theme of in-form players, Emiliano Grillo should go well.

The Argentine has been playing nicely all spring and while some of his golf in contention has been poor - most notably in the Indian Open - unlike that week we're not being asked to take short prices. Should he contend at 80/1 and come up just short, so be it.

The positives certainly outweigh the growing frustration surrounding his inability to win a second PGA Tour title, and they centre around driver which is definitely a weapon for a player who ranks 16th in strokes-gained off the tee.

Glance down leaderboards here and you'll see many of the world's best drivers, so the fact that Grillo is long enough not to be left behind and straight enough to stay out of trouble highlights that Quail Hollow should suit.

Click on the image of Grillo for Sky Bet's 8 places market

Truth be told, he's not shown that here just yet but did figure prominently in the ball-striking charts when last the Wells Fargo was played here in 2016, and perhaps significantly the leader in greens that week was Chris Stroud, who was down the field too only to step up and contend on his next visit in the PGA.

Furthermore, among the courses which best correlate with Quail Hollow may well be Bethpage Black, where former Wells Fargo champ Lucas Glover won the US Open in 2009 and where Grillo finished second to Reed in the 2016 edition of The Barclays.

His form at Muirfield Village in the Memorial Tournament is similarly noteworthy and six top-20 finishes this season, including third in Houston just prior to the Masters, suggest that he is playing well enough to take advantage of the right set of circumstances.

Others for the shortlist include Ollie Schniederjans, who was second on his last start in North Carolina but isn't driving the ball well enough to inspire confidence, whereas Lucas Glover and Kyle Stanley seem likely to play well without quite threatening to win, a comment which may also apply to the back-to-form Nick Watney.

Instead, I'll finish with the rock-solid Tony Finau and the wildly speculative Robert Streb.

Finau has finished 16th and 28th here in the Wells Fargo and fared reasonably well in last year's PGA Championship, so with last week's effort in New Orleans appearing to confirm that his ankle has recovered there's every hope he'll work his way into contention.

Another big-hitter who figures prominently in the driving and par-five scoring statistics as you'd expect, Finau looks close to his second PGA Tour title having twice finished second this season, and his last solo start was an excellent 10th at Augusta to secure a Masters return in 2018.

The strength of this field is holding up his price enough for concerns around his conversion rate to be overlooked and, like Hadley, he looks set to relish a return to worrying about just his ball on what appears to be an ideal golf course.

Streb is among the rank outsiders because he's been in abysmal form, but he wasn't playing well prior to finishing second in the Greenbrier last summer and, just like that event, he boasts a deep bank of positive course form at Quail Hollow, including fourth in 2015 and 22nd in the PGA Championship.

Chances are he's simply not in the sort of shape required to take advantage of his comfort levels here, but the arrival of his son last week could just inspire a big upturn in form and, given the venue and his price, that's enough to justify a small bet. Should the price dip beneath 300/1, I'd suggest ignoring all of this and focusing instead on the solid each-way credentials of the previous quartet.

Posted at 2100 BST on 30/04/18.