On a recommendation, Walker went to Chile and signed with First Division Club, Universidad Católica. They loaned him out to Club Deportivo Huachipato of Chile's First Division in 1998, in which we was named Team MVP, then U. Catolica brought him back the following year. He became the starting goalkeeper for the club, playing in multiple Copa Libertadores tournaments, which included wins against Argentina's Boca Juniors and Brazil's Flamengo. From 1997-2002, Walker broke numerous national records for Universidad Catolica. In 1999, U. Catolica finished runners-up in the Chilean National Championship. In 2001, Walker received Chilean Goalkeeper of the Year honors, while U. Catolica finished Runners-Up in the Chilean National Championship. That year, U. Catolica advanced to play in Copa Mercosur for the fourth straight season. They also competed in the Copa Libertadores. In 2002, Walker was named Best Goalkeeper of the Chilean Apertura National Championship as well set a Club record going 708 minutes (almost nine games) without being scored on, a record that held until 2008. Also in 2002, Walker led U. Catolica to win the Chilean Apertura National Championship. He was also named Best Goalkeeper in Round One of prestigious South American Championship, Copa Libertadores, later that year.