Walker was a stylish hurler who in 1929, his second full season, went 14-7 for the Giants with a league-leading 3.09 ERA. He led in ERA again in 1931 (2.26), going 17-9 with a league-high six shutouts. A native of East St. Louis, he was traded to the Cardinals in October 1932. He missed two months of the championship 1934 season but chipped in 12 wins. Pitching in relief in the 1934 World Series, he was the loser in Games Two and Four as the Cardinals defeated Detroit in seven.