Is the reason that Rory McIlroy switched drivers this week because the driver he had been using was deemed non-conforming by the USGA during random club testing? That’s the rumor – unconfirmed so far – that began floating around Friday afternoon.

The USGA tested Rory McIlroy's driver and concluded that it did not meet established standards, forcing him to change it before the PGA Championship.

McIlroy opened his campaign at Quail Hollow with a disappointing three-over-par 74. Despite beginning with a birdie on his first hole, the par-five 10th, the Northern Irishman struggled to find rhythm.