Rory McIlroy arrived at Royal Birkdale on the back of three consecutive missed cuts. And at the halfway stage of his opening round it looked certain that he would be making it four in a row.

On the eve of the Open, McIlroy had spoken in detail about how the greatest players were able to separate themselves from their rivals more by their mental powers than their physical ones.

“The two best players ever, Tiger Woods and Jack Nicklaus, were both so strong mentally,” he said. “So that tells you maybe the separation factor is the mental side of the game, and being maybe a little bit better in that aspect than the rest of the guys. But I think it’s really about knowing yourself and knowing what works for you and what thoughts work and what techniques work.”

By the time he had reached the 6th green, McIlroy was one-handing a putt in for a fifth bogey. It seemed like he had practically played his way out of the tournament. His body language suggested that he knew it only too well.

Open comment Rory Birkdale

Meanwhile, despite the more difficult morning conditions, Jordan Spieth had posted a 65. At -5 he was fully 10 shots ahead of the Northern Irishman at that stage.

Spieth may not have a long game to match his rival’s at its best – but he is streets ahead when it comes to getting the most out of his game on a regular basis.

As for McIlroy, it is now three years since his fourth and most recent major came at Valhalla, on the back of his Open success at Hoylake.

At that stage, he was the best player in the world. The talk was of him rivalling Tiger Woods’ haul of 14 majors.

“I think when you ride on the crest of a wave, it’s easy to get caught up with those expectations and you start believing them,” he said.

“And of course, I have been able to play golf in stretches that if I continued that type of golf for six, seven, eight years, yes, I would be able to win a lot more.”

To be a truly great player, though, you have to be slightly better than relying on crests of waves to win your majors in bursts.

When McIlroy is hot he is the best golfer in the world. However, the suspicion remains that he struggles to haul himself into contention when the stars are not aligned.

More than any other major, the Open calls for doggedness and resilience. The conditions are ever-changing and as a golfer you have to be unflappable and adaptable.

That’s what Spieth showed evidence of here.

Rory struggles Spieth

Starting his round in squally, dank conditions, from the moment he recovered from damp rough to the right of the 2nd by firing his recovery into 10 feet and inevitably draining the putt for a three, the Texan was rarely in trouble.

A bogey-free 65 was an outstanding round of golf. And one that looks ominous for the rest of the field.

McIlroy struggles

By contrast, McIlroy looked a beaten man long before he turned in 39.

It was greatly to his credit, then, that inward birdies at the 10th, 15th, 17th and 18th turned what felt for all the world like a 77 into an almost creditable 71.

Although superficially upbeat, there had been something slightly unconvincing about his performance in front of the media the day before. When you acknowledge that you play your best golf when on the crest of a wave but arrive on the back of three missed cuts, it’s hard to be too optimistic.

McIlroy acknowledged as much himself: “It was Tom Weiskopf who first said: ‘When I’m playing well, I can never imagine how I ever played so badly. And when I play badly, I can never imagine how I played so great.’ And I think that’s how fine the line is in golf, between playing great and playing poorly.”

True, McIlroy’s class is permanent, but to rectify his current poor form he needs something to feed on. Perhaps that back nine of 32 will come to be seen as a turning point in his season.

Rory struggles Els

Should he want some inspiration on how to deal with adversity then he need look no further than Ernie Els.

Last April, the fellow four-time major champion suffered the humiliation of six-putting the 1st green at Augusta, his hands at the mercy of the dreaded yips. There is said to be no way back.

Yet, at the age of 47, the Open champion of 2002 and 2012 is proving otherwise as McIlroy struggles. He could so easily have quietly disappeared from top-level golf. Instead he continues to strive on the PGA Tour and here at the Open Championship, playing in his 99th career major.

He rolled back the years with a two-under-par 68 to sit just outside the top 10.

Unlike Rory – for the time being at least – this is a past champion who is right in contention to add another Claret Jug.

For more from Royal Birkdale, check out our dedicated Open site.