(AP) - Tiger Woods has withdrawn from the opening FedEx Cup playoff event with what he calls a mild oblique strain.

Woods opened with a 75 on Thursday in The Northern Trust. He says his oblique muscle caused him mild pain and he went for treatment Friday morning. He says it wasn't enough for him to play the second round Friday afternoon.

It's the first time this year Woods has withdrawn in the middle of a tournament.

He says he hopes to be able to play next week in the BMW Championship at Medinah, where he won two of his PGA Championships.

If he plays next week, Woods would need to move back into the top 30 in the FedEx Cup to be able to defend his title at the Tour Championship, where last year he won to cap off a remarkable return following four back surgeries.