At the rate American golf stars are getting hurt, Tom Watson might become a playing captain when his US Ryder Cup squad tries to reclaim the trophy from Europe next month.

Sixth-ranked Matt Kuchar, already set for the roster based on qualifying points, withdrew before Thursday's start of the PGA Championship at Valhalla with back spasms.

Dustin Johnson had been set for a spot before announcing last week he would taking a leave of absence through the end of the year, with a Golf.com report saying he tested positive for cocaine and was set for a suspension.