 Walker came back to the US later that year, signing with the MetroStars, after starting goalkeeper Tim Howard signed with Manchester United.In 2003 with the MetroStars, Walker became the third goalkeeper in MLS history to finish a season with sub-1.00 Goals Against Average (GAA), capturing the league-best 0.95 GAA.That same year, Walker was the MLS Player of the Month for August and the MetroStars finished as Runners-Up in the US Open Cup.