CHARLOTTE, N.C. -- Rory McIlroy was part of roughly 50 players whose drivers were tested before the PGA Championship, which was described Saturday as a normal procedure designed to protect players who are not aware if their clubs have exceeded limits. McIlroy drew particular attention when Sirius XM PGA Tour Radio reported Friday afternoon that his driver was deemed nonconforming and the Masters champion could no longer use it at Quail Hollow. McIlroy has not spoken to the media the last two days. Kerry Haigh, chief championships officer for the PGA of America, confirmed the USGA was asked to test drivers at the PGA Championship. The USGA, which governs golf in the U.S. and Mexico, regularly conducts tests on the PGA Tour when asked. Results are confidential. Haigh said the standard process is for one-third of the 156-man field to have driver tests and that was the case at Quail Hollow. "Finding driver heads that have crept over the line of conformance is not an unusual occurrence, especially for clubs that are hit thousands of times over a long period of time," Haigh said in a statement. "The results are kept confidential to protect players, who are unaware the club has fallen out of conformance and not responsible for it falling out of conformance other than hitting the club thousands of times." Drivers that exceed USGA limits, particularly when the face gets too thin and can cause a slight trampoline effect, need to be replaced. Haigh said players change "without issue." "To publicly identify players whose club did not conform can lead to that player being questioned unnecessarily," Haigh said, referring to why results are confidential. "Neither the USGA nor the PGA of America have any concerns about player intent." Some companies tend to make the face as thin as possible, within limits, for greater distance. When constantly hit at swing speeds around 115 mph, topping 120 mph for the power players, that can allow a club to become nonconforming, known as "creep." Research indicates a driver can start to creep after 5,000 swings, which is typically about four months depending on how much play or practice is involved. McIlroy drew extra attention because he was last among the 74 players who made the cut in driving accuracy, hitting only 10 fairways over 36 holes. It was at least the second time that results of a random driver test have been reported. Xander Schauffele had to replace his driver at the 2019 British Open and he was furious with the R&A for not keeping the matter private.