The problems continued to mount for US Ryder Cup captain Tom Watson in the early stages of the US PGA Championship on Thursday, even though Tiger Woods was fit enough to take part.

Just days after withdrawing from the final round of the WGC-Bridgestone Invitational with a back injury, Woods declared himself pain free after nine holes of practice on Wednesday and teed off at 8:35am local time alongside Phil Mickelson and Padraig Harrington.

But fellow American Matt Kuchar was not so fortunate, the world number six pulling out after suffering back spasms as he warmed up on the range. Dustin Johnson has already declared himself unavailable for Watson's team to deal with "personal challenges", while defending US PGA champion Jason Dufner is struggling with two bulging discs in his neck.

Kuchar, who has already sealed his place on the Ryder Cup team for Gleneagles, was replaced in the draw by first reserve John Huh, who teed off at 9:05am alongside major champions Louis Oosthuizen and Justin Rose.