Tiger Woods has been world number one for 279 consecutive weeks
Tiger Woods has raised doubts about his participation in October's Ryder Cup at Celtic Manor in Wales after enduring his worst finish as a professional.
The American ended the WGC-Bridgestone Invitational 18 over, although he keeps hold of the world number one spot.
"I wouldn't help the team if I'm playing like this. No-one would help the team if they're shooting 18 over par," a rueful Woods told reporters.
"I think I can turn it around. We have lots of time between now and then."
Woods sits 10th in the United States Ryder Cup list and will miss out on automatic selection unless he performs well enough at this week's USPGA Championship in Wisconsin.
If he fails to rise into the top eight, he would then have to rely on a wildcard pick from US captain Corey Pavin if he is to feature in the biennial event from 1-3 October.
"Shooting 18 over par is not fun," said Woods. "I don't see how it can be fun shooting 18 over, especially since my handicap is meant to be zero. It's tough.
"I need to hit the ball better, I need to chip better, I need to putt better. It has been a long year."
Woods shot a final-round 77 in Ohio to finish joint 78th in the 80-man field at the Firestone Country Club.
His five-year reign as world number one would have come to an end if Phil Mickelson finished fourth or better.
But Masters champion Mickelson carded 78 on Sunday to finish in a tie for 46th behind winner Hunter Mahan.
Woods's final-round slump ended a dismal week which saw him card 74, 72, 75 for the first three rounds as he posted his highest 72-hole score in relation to par.
But Mickelson failed to take advantage, ending on three over for the tournament with rounds of 66, 68, 71 and 78.
Despite missing out on Woods's number one tag, Mickelson remained confident that he would take his compatriot's title soon.
"I hit some wild shots and the round seemed to get away from me," he said. "If I keep playing, it will eventually happen but I've got to get in a better rhythm. I've not played a lot and it showed."
The Firestone Country Club had previously been a happy hunting ground for Woods, who has won seven out of his 10 tournaments played there.
Yet this year his combined total of 298 was 39 shots higher than the record he set for the course 10 years ago.
Only Sweden's Henrik Stenson kept Woods from finishing in last place.