Xander Schauffele told reporters that he thinks Scottie Scheffler is using a back-up driver as well as Rory McIlroy after a report emerged on Friday that McIlroy's driver failed a USGA test earlier this week.
The PGA of America issued a statement on driver testing on Saturday, where it said that it had requested the USGA to test around a third of the field's drivers this week and that all results were confidential.
