Brooks Koepka credits coach Pete Cowen for return to form as he leads in Memphis

Defending champion Brooks Koepka carded a superb eight-under-par 62 to take a two-stroke lead after the first round of the WGC-FedEx St Jude Invitational in Memphis on Thursday.

The four-time major winner made a blistering start with four straight birdies and recovered from a bogey on the seventh to pick up further shots on the eighth and ninth to reach the turn in 30.