RORY McILROY will attempt to become just the second player in the modern era to successfully defend the US PGA Championship this week, but will do so armed with a healthy new perspective.

McIlroy feared he had broken his ankle while playing football with his friends on July 4, but a ruptured ligament was serious enough to prevent him defending the Open Championship at St Andrews and WGC-Bridgestone Invitational in Akron.

The 26-year-old thought he would be unable to bring himself to watch his rivals do battle for the Claret Jug, with Jordan Spieth narrowly failing to win the third leg of an unprecedented calendar grand slam before Zach Johnson eventually triumphed in a play-off.

However, McIlroy was surprised by his reaction to events at the Old Course as he battled to get fit enough to return to competition at Whistling Straits, where he finished a shot outside the play-off in 2010.

"I honestly thought it was going to be harder than it was. I thought I was going to miss it more than I did," said McIlroy, who will play alongside Spieth and Johnson in the first two rounds. "But if anything, having to sit those tournaments out, especially the Open Championship going back to St Andrews, which is probably my favourite venue in the world, it gave me a huge sense of perspective.

"When you're playing week in, week out and you're thinking about winning these tournaments, you get so wrapped up in what you're doing and your own little life and your own little bubble; sometimes you forget there's a bigger, wider world out there.

"No matter whether you win a golf tournament or not, people are going to get up on Monday morning and go to work and do their daily things and honestly not a lot of people care.

"Obviously it means a lot to you and people involved in golf, but in the big scheme of things, it's not life or death.

"And that's something that I can bring in with me this week, knowing that, okay, it's a big deal, but no matter what happens this week, only a very small percentage of the population really care."

McIlroy insisted he would not give up playing football and revealed he was taking two-hour walks within two weeks of the injury occurring in his "fourth or fifth game in a 10-day period", but admitted he would need to take precautionary measures for the rest of his career.

"I thought I broke it because as soon as I went over on it I heard like a snap," the four-time major winner added.

"Obviously that was the ligament that snapped. I looked down and 30 seconds later it got the size of a tennis ball, basically because all the fluid came out of the joint capsule.

"When I got the scan that night it showed that I totally ruptured one ligament and I had a grade two [tear] in the other. If that had been a total rupture then that would have required surgery.

"It was always going to be a six-eight week injury. Then it just depends on the individual. As injuries go, it could have been worse.

"The ligament that I ruptured, I don't have that any more. So I've only got two ligaments on the outside of my ankle instead of three. It's just about trying to strengthen the ankle and maintain as much integrity in it as possible. But it's really not anything to be concerned about in the long term."

Since the US PGA became a stroke play event in 1958, only Tiger Woods in 1999-2000 and 2006-2007 has won back-to-back titles.

But McIlroy will aim to convert his superb tournament record – since 2009 he is a collective 34 under par, 17 shots better than anyone else – into a third title in four years following wins at Kiawah Island in 2012 and Valhalla last year.

"I think more than anything else the golf courses that we have played in this tournament have been set up in such a way that it suits my type of game and it really rewards good driving," McIlroy added.

"I think it's usually a fair test of golf, somewhere within 10 to 15 under par usually wins. It's not like it prevents the guys from making birdies, but it still penalises you if you don't hit good shots.

"My expectation levels are the same. I've been practising for over three weeks, getting my game ready, getting my game sharp. I feel like I'm playing well. I don't see any reason why I can't bring the sort of form that I've shown in practice rounds and on the range to the tee on Thursday afternoon."