Vikings receiver Troy Williamson underwent a medical procedure earlier this week to remove an abscess from his left hip and will not participate in this weekend's mini-camp, coach Brad Childress said this morning. Williamson, the Vikings' top draft choice in 2005, worked with the first team during the Vikings' first veteran mini-camp last month. Childress said he had no reason to believe Williamson won't be ready for training camp when it opens in late July.