On defense, Walker recorded 5 interceptions during his career, which he returned for 62 yards. His main contributions came as a punt and kickoff returner on special teams, recording a total of 145 punts returns for 1,437 yards and 167 kickoff returns for 3,779 yards and a touchdown. Walker's best season was in the strike shortened 9-game season of 1982, when he recorded 3 interceptions on defense and 433 kickoff return yards, assisting his team to a championship appearance in Super Bowl XVII. In 1985, he recorded an NFL record 692 punt return yards. This would stand as a record until 1996 when it was surpassed by Desmond Howard's 870 yards.
Walker is best remembered for his performance on special teams in Super Bowl XVII and Super Bowl XIX. In Super Bowl XVII, Walker recorded 4 kickoff returns for 190 yards and a touchdown, setting Super Bowl records for most kickoff return yards and highest single game yards per return average(47.5). This included a record 98-yard kickoff return for a touchdown in the second quarter, the first kickoff ever to be returned for a touchdown in Super Bowl history. He also had a 42-yard return that set up a Dolphins field goal. His contributions helped the Dolphins maintain a lead in the game until late in the fourth quarter, despite Miami quarterback David Woodley being limited to just 4 completions in the entire game. In Super Bowl XIX, Walker contributed 93 kickoff return yards and 15 yards returning punts.