Woods won last year's USPGA at Medinah

The world number one fired three birdies in his first six holes after starting from the 10th but stumbled with a bogey on 18.

Two further bogeys dropped him back to level by the 13th.

He made amends on 14 but dropped shots at the 7th and 8th holes soured the 12-time major champion's opening round.

"I thought I hit the ball better than I scored," said Woods, a three-time USPGA champion.

"The greens were softer this morning and the wind was blowing a little bit but at least it was from the same direction. But I had a tough time on the back nine with the wind."

Woods, who romped to the WGC Invitational title last week, is yet to win a major in 2007 but insisted that did not add to the pressure this week

"I just have to go out there and play and grind it out like I normally do," said the 31-year-old, who has won four PGA Tour events this season and finished second in the Masters and US Open.

Woods has completed only three seasons without a major title since turning professional in late 1996.

He failed to win a grand slam event in 1998 after embarking on the first swing change of his career and failed to claim a major in 2003 and 2004 while going through a second swing overhaul.