Danny Willett believes Rory McIlroy has been handed a potentially vital advantage in the battle to end the season as European number one.

The ankle injury which forced McIlroy to sit out three tournaments this summer, including the defence of his Open title at St Andrews, means he will not play the 13 events usually required to remain in the Race to Dubai, where he leads Willett by just 1,613 points.

However, European Tour chief executive Keith Pelley cited ''exceptional circumstances'' in granting McIlroy permission to remain on the money list by playing 12 events as he tries to win the Harry Vardon Trophy for the third time in four years.

McIlroy is therefore eligible for a share of the five million US dollars bonus pool and his presence also affects the top 30 on the money list on November 15 who qualify for next year's Open, the top 60 who make this week's season-ending DP World Tour Championship and the 110 players who kept their card for next season.

Willett, who would also be entitled to significant bonuses from his sponsors if he won the Race to Dubai, believes Pelley made the "right decision," but feels a rested McIlroy has the upper hand at Jumeirah Golf Estates.

"Obviously playing a lower amount of events than what's required was one of the main benefits I would have said for Rory with how things panned out," said Willett, who has played 22 events to McIlroy's 11 and described himself as "stale" during last week's BMW Masters, which McIlroy did not play.

"I appreciate that him playing makes a massive difference for the Tour and you have to kind of let him off with the events, but certainly he has more of an advantage over the guys who have played all three (in the Final Series) and this will be the fourth.

"There's a lot of travelling, a lot of golf, time changes, sleeping patterns; everything like that can really take its toll, especially at the end of a season. I think having had a week off might have benefited him.

"If Rory wins more money than anyone else playing less events, then that's just good golf. There's still rules there to kind of abide by, otherwise they wouldn't make rules. If rules were allowed to be broken all the time, then there's no point in setting them in the first place.

"But in that case it's a very difficult one to get correct and it was the first decision Keith had to make in becoming the chief executive of the Tour. I think he made the correct decision.

"I can't really say a great deal more. It doesn't really change how we are going to approach this week so we're just going to go out there and try and win."

McIlroy said in October that he had to take a "selfish view" of his exemption and stressed on Tuesday that he was not concerned about the prize money or his share of the bonus pool.

"I'd gladly take the trophy and they can keep the money and do whatever they want with it," McIlroy said. "It's more about trying to win The Race to Dubai again. It's always a goal of mine. At the start of the year, I want to be at the top of these lists at the end of the season, whether it's the Race to Dubai or whether it's the FedEx Cup.

"The Race to Dubai reflects the way you've played through the entire season, and somehow that's true. I feel like I've gained most of my points in the first half of the season with my performances.

"I've just sort of held onto that position a little bit. Coming into this week and not having wrapped it up like I had done the previous two times I've won, there is more intensity. It would be a really great way to finish the season, and knowing that I haven't already got it wrapped up, it focuses the mind and I really want to play well this week."

A total of seven players can still win the Race to Dubai, although Justin Rose, Shane Lowry, Louis Oosthuizen and Branden Grace need to finish second or better at Jumeirah Golf Estates, while Byeong Hun An has to win.

And they will all have to get the better of course-specialist McIlroy, who has recorded five top-five finishes in six appearances, including a victory in 2012 which sealed his first Race to Dubai title and finishing second behind Henrik Stenson last year.