During his rookie season in Philadelphia, he recorded 11 regular season wins and a victory in Game One of the 1980 World Series, his Phillies defeating the Kansas City Royals in six games. Traded to the Braves, he bounced between the main club and AAA until being released in March 1984. He was signed to a minor league contract by the Pirates and led the Pacific Coast League in ERA and wins in 1985, earning a trip back to the majors. He was named to the All-Star team in 1988 when he won 12 games and posted a 2.71 ERA.
In his waning years, Walk served as a spot starter and swingman for the Pirates' teams that won three straight NL East titles from 1990-1992. His most memorable outing being when manager Jim Leyland removed him from the bullpen and named him a surprise starter in Game Five of the 1992 NLCS against Atlanta. He tossed a complete game three-hitter to stave off elimination in a series which the Pirates would eventually lose in seven games. He was also the pitcher who was warmed up in the bullpen when Francisco Cabrera hit the two-run, game-winning single against Stan Belinda, which won the series for Atlanta. Despite both Walk and Cabrera being right-handers, Leyland opted to keep Belinda (despite having walked Berryhill to load the bases and giving up a deep fly ball to Ron Gant) to pitch to Cabrera.
He is currently an announcer for the Pittsburgh Pirates on Fox Sports Pittsburgh and radio.
In April of the 2008 season, Walk made some scathing comments regarding the career ejections record which is held by Bobby Cox. Some circles believe that Walk made these comments, because he is still angry over Cox not having him called up from AAA for long in 1981, when Walk was with the Richmond Braves.