Walls signed with the Denver Broncos after going undrafted in the 2002 NFL Draft. After his signing, Walls became the tallest cornerback in the NFL at 6'4". He played in 13 games as a rookie in 2002 and recorded six tackles all on special teams. His only defensive appearance came against Baltimore, however his only stats of the game came on special teams with two tackles. His first forced fumble was against the St. Louis Rams. In 2003, Walls started all 16 games and ranked fifth on Denver with 68 tackles and led the team with 20 pass breakups. His 20 pass breakups were the most in Denver history since Ray Crockett had 21 in 1997. Against San Diego he had six tackles while against Cincinnati he had five tackles and three pass breakups. In the AFC Wildcard game he recorded three tackles and a forced fumble. In 2004, Walls played in seven games and had 21 tackles along with two pass breakups. He was later placed on injured reserve with a shoulder injury. In his season debut on September 12, he recorded four tackles before suffering the shoulder injury. After the injury, he played sporadically, either missing whole games or leaving in the fourth quarter or earlier. In his final season in Denver, Walls had 16 tackles in seven games, with his final appearance as a Bronco coming against the New York Giants on October 23, 2005. He was placed on injured reserve with a groin injury on November 5, 2005.
Walls signed a one-year deal worth $1.75 million with the Kansas City Chiefs on April 1, 2006. He played in all of the Chiefs 16 games and started two. In his 16 games he had 29 tackles. After the 2006 season his contract expired and he was not re-signed.
St. Louis Rams
On April 4, 2007, he signed with the St. Louis Rams as an unrestricted free agent. Walls played in five games and recorded nine tackles. He was waived on October 12, 2007.
Baltimore Ravens
Walls signed with the Baltimore Ravens on May 20, 2008. He was released at the end of training camp.
Calgary Stampeders
Walls signed with the Calgary Stampeders on September 22, 2008. His first two weeks with Calgary were spent on the practice roster before being activated and starting against the Saskatchewan Roughriders on October 13. Against the Roughriders he led the Stampeders with nine tackles and recorded his first interception in the CFL. After his debut in Calgary, he started every game for the rest of the year. In all of his starts with the Stampeders he got multiple tackles. He ended up with 23 tackles on the year but missed the playoffs including Calgary's 96th Grey Cup victory with an injury.
On May 15, 2009, Walls was traded to the Winnipeg Blue Bombers.
Edmonton Eskimos
After one season in Winnipeg, Walls signed as a free agent with the Eskimos on March 22, 2010. He was released during the following off-season on May 27, 2011.
