Day (back) withdraws from Tour Championship

ATLANTA -- Jason Day's PGA Tour season officially ended two days earlier than expected, when he withdrew from the Tour Championship due to a lingering back injury midway through the second round on Friday afternoon.

"The injury is a strained ligament in his lower right back with a muscle spasm. He withdrew as a precautionary measure," read a statement from Day's management team.

It is the same back injury that forced Day, the world's No. 1-ranked player, to withdraw from the BMW Championship two weeks ago.

"I put the tee in the ground at the BMW Championship, and my back went out," Day explained earlier this week. "Last time it went out, I changed a diaper. So it's nothing where I go and…