Jason Day feels good. Well, make that just okay.

After having to withdraw from the final round of the BMW Championship two weeks ago with a back injury, Day shot a 3-under 67 in the first round of the Tour Championship on Thursday at East Lake Golf Club. He is tied for fourth, one shot off the lead.

Day said he felt a sharp pain on several swings.

“I know when it’s there and when it may come,” Day said. “When I get to the top of the swing, as soon as my hips start to unfold and then there’s a bit of separation. It just crunches down. It just hurts.”

Day first injured his back changing a diaper, oddly enough. He re-injured it putting a tee in the ground at the BMW Championship, the third event in the FedEx Cup playoffs that culminate this week at the Tour Championship. He was forced to withdraw from the event.

Day said an MRI exam revealed an annular tear of a disc in his back.

“In a perfect world, I would love to have two weeks off where I can just really try to settle the back down,” Day said. “It’s not 100 percent, but who is 100 percent out here who’s playing right now?”