The bigger question is whether the world's No. 2 player can compete.
'Put it this way,' Furyk said from his home in Ponte Vedra Beach, Fla., 'To me, playing and competing are two different things. Could I play tomorrow? If I had to get it done, I could. But could I compete? I don't feel right now I could compete tomorrow. That being said, I have a week from today until I have to compete. I'm expecting my body to respond well.'
Furyk lost in a playoff at the Colonial and finished one shot behind Angel Cabrera in the U.S. Open. He picked up his first victory of the year on Sunday at the Canadian Open, where he made a hole-in-one during his final round 64 to win by one shot over Vijay Singh.
But while hitting balls on the range at Firestone on Tuesday, Furyk said he felt a twinge in the middle of his back that didn't feel right.
'It started tightening up on me, and it continued to get tighter and tighter,' he said. 'I went to the (fitness) trailer and started to get it worked out, but Tuesday night it was at its worst.'
Furyk said his back made progress during treatment on Wednesday, but after another session Thursday morning it did not feel good enough to allow him to compete at Firestone. He was not replaced in the field of the World Golf Championship.
He consulted with doctors and physical therapists that he sees regularly, on the PGA Tour and in St. Louis, to let them know what happened and how he felt.
'It seems like everything will be fine,' he said. 'I'll keeping getting treatment and fly to Tulsa on Sunday. We will see. I'm usually a pessimist, but I felt so much better yesterday and today, and I feel pretty optimistic.
'I'm just a dumb golfer, but I'm a pretty good patient.'
Furyk had to withdraw from the Barclays Classic last year at Westchester Country Club -- like Firestone, one of his favorite stops on the PGA Tour. He played the following week in the U.S. Open at Winged Foot and finished one shot behind Geoff Ogilvy.
'In the long run, I'll get to play a lot more in Akron and Westchester. It's important now to make sure I'm healthy,' he said.
The one thing keeping his spirits high is that victory in Canada, the 13th of his PGA Tour career that allows him to start next season at Kapalua for the winners-only Mercedes-Benz Championship. Furyk has a home on the Plantation Course at Kapalua.
'At least I'm in a good frame of mind from winning,' he said. 'If I had lost in a playoff and couldn't play, I'd be really upset.'