'I've very stiff right now, don't have a lot of movement in my upper back and then into my neck,' Furyk said.
The injury comes two days after Furyk won the Canadian Open with a 64 in the final round, his first victory of an otherwise steady season that moved him up to No. 2 in the world ranking.
The Bridgestone Invitational, which starts Thursday at Firestone, is one of his favorite events of the year. He lost in a seven-hole playoff to Tiger Woods in 2001, and finished one shot out of a playoff last year, which Woods won over Stewart Cink.
'Right now, I don't know whether or not I'll be able to play,' Furyk said. 'I'll make that decision probably tonight and see how things are going. I'm a little disappointed after playing so well last week, and coming to a place that is in my top five events. But obviously, the first thing is getting healthy.'
Also in doubt was the PGA Championship next week at Southern Hills, where Furyk figured to be among the favorites. He has not finished worse than 15th in the majors this year, including a runner-up finish at Oakmont in the U.S. Open.
Furyk said he was hitting balls Tuesday at Firestone when his back began to tighten up.
'I quit hitting balls as quick as I could and tried to get up here to the physio therapy trailers to try to get some treatment,' he said. 'But last night, it was very tight and relatively painful.'
Furyk also had a sore back before the U.S. Open at Winged Foot last year, where he tied for second. He said that was in the upper back and made it difficult for him to turn to the right. This injury was to the lower back and made it hard for him to turn to the left.
'I had gone through my irons and was on the driver, and just made a swing where it didn't feel right,' he said.