Ruiz retired in 2005 when he lost to James Toney, but came back 10 days later when Toney failed a steroid test. He lost the title to 7-foot, 324-pound Nikolay Valuev in December 2005, a controversial decision that had the Berlin crowd booing. In 2006, he lost a split decision against Ruslan Chagaev in Dusseldorf, Germany.