Kenechi Udeze, the Vikings defensive end who missed last season because of leukemia, has retired. Coach Brad Childress said Wednesday that Udeze, the team's first-round draft choice (20th overall) in 2004 out of Southern California, has ended his comeback attempt. Udeze tied for the team lead in sacks in 2007, but got sick following the season and was diagnosed with acute lymphoblastic leukemia (ALL) in February 2008. He had a bone marrow transplant last July and felt well enough to participate in this spring's minicamps and organized team activities. But after the practices, Udeze apparently decided he needed to devote his time to fighting his illness. After a June workout, he told the Star Tribune: "I'd be lying if I said it was easy. There was never an easy point. The first time I went back to USC and started working out with the fellas, I fell. I took two steps and I fell. I took small steps at first and, to where I am now, I can't complain."