Despite back problems, the 34-year-old shot a 68, two under par, on the first day of play at Royal Birkdale.
The injury occurred at the gym on Wednesday morning.
I was in a stretching position and sneezed - and my back didn't like it, he says.
It's like a pinched nerve in the lower back.
He says he won't throw in the towel.
No matter how much it hurts, I'll bite the bullet. But of course it has to be playable.
