Tiger Woods could still play in this week's US PGA Championship after his agent revealed it was "way too early" to make a decision on the 14-time major winner's back injury.

Woods became a doubt for the year's fourth major when he withdrew from the WGC-Bridgestone Invitational during Sunday's final round.

The 38-year-old looked in severe pain from his back after hitting his tee shot on the 494-yard ninth and was soon leaving the course, prompting questions over both his long and short-term future.

But Woods' agent Mark Steinberg confirmed on Monday night that a decision was yet to be made on his participation at Valhalla, although Tuesday's press conference, scheduled for 9.30am local time, was postponed.

"Way too early," Steinberg said in a text sent to reporters.

"He has to rest and get treatment and then assess later. Pointless to make that decision now without proper time to give him best chance.

"Nothing further today, maybe (not) even tomorrow."

Woods was playing just his third tournament since undergoing microdiscectomy surgery on 31 March when he withdrew in Ohio and has not won a major since the 2008 US Open.

He had previously spoken about being "pain-free" for the first time in two years, but said on Wednesday that other people who had undergone the same surgery "had no idea" how he was able to play again so quickly.

Should the current injury prove to be serious, Woods would be a major doubt for next month's Ryder Cup.

United States captain Tom Watson has already stressed that Woods does not merit a place on the team simply by being healthy enough to swing a club and admits his current problem could further damage his chances of selection.

"Tiger would be a great addition to our team," Watson told PGA Tour Radio.

"As I've said all along, I would pick Tiger Woods if he's healthy and playing well.

"This doesn't bode well right now.

"I just hope that maybe it's just an isolated problem that he can turn around and possibly play this week at the PGA."