Rory McIlroy was dealt a blow just days before the start of this week’s PGA Championship, it has been revealed.

The recently crowned Masters champion was forced to switch drivers here at Quail Hollow after his was deemed to be nonconforming by the USGA on Tuesday, according to XM Sirius PGA Tour Radio.

McIlroy is arguably the best driver in golf. Using the TaylorMade Qi10 driver, he came into this week at the top of the rankings for strokes gained off the tee and third in driving distance so far this season.

The USGA randomly tests clubs to make sure they are conforming at the request of tournaments in the US and Mexico and, while the exact issue has not been reported, McIlroy’s was deemed to be ineligible.

The USGA confirmed they did testing at Quail Hollow when asked to do so by the PGA of America. All tests are done before the first round and results are supposed to be confidential.

The tests typically are random, and it is not unusual for testing ahead of major championships. Drivers often can fall outside the limits after a lot of use.

Rory McIlroy was forced to switch drivers after his was deemed to be nonconforming

The Masters champion made the cut on the number after a bogey on the final hole

‘That program is consistent with the same level of support that we provide to the PGA Tour as part of their regular program for driver testing,’ the USGA said.

Former PGA Tour golfer Johnson Wagner came to McIlroy’s defense on the air. He said: ‘The USGA conducts these tests pretty much every year out here. They test all aspects of the face, and drivers fail all the time. Every single week, someone’s driver fails.

‘It is by no fault of the player, they don’t know how to do it, it is a sophisticated testing system. When you are a player like Rory McIlroy, who hits the ball as hard as he does, the face naturally thins out.’

McIlroy’s driving has been unusually wayward so far this week. He was tied for last in driving accuracy among the 74 players who made the cut, hitting only 10 fairways in two rounds.

The Grand Slam winner only managed to secure his place at the weekend on the final hole of his second round after bogeying both 17 and 18 on Friday evening.

He certainly didn’t make it easy on himself after missing a short putt on the par-3 17th and then hitting his drive off the roof of a concession stand on the left side of the fairway on No. 18.

Fortunately for McIlroy his ball came to rest just a few feet from the creek that runs up the left side of the final hole, avoiding a potential drop and penalty stroke.

For the second straight day, McIlroy left Quail Hollow and declined to speak to the media.