After pitching in the major leagues, he returned to Carnegie Tech as football coach in the fall of 1913, and played professional basketball that winter for Pittsburgh. In 1913, Walker returned to Major League Baseball as a pitcher for the Brooklyn Superbas. He appeared in 11 games for Brooklyn in 1913, pitching 58 1/3 innings and compiling a 3.55 earned run average. In August 1913, The Pittsburgh Press wrote of Walker: "Fred Walker, otherwise known as 'Mysterious Mitchell,' who is pitching for Brooklyn, appears to be a perfectly good topnotcher for about four innings. After that—well, he hasn't won any laurels as a stayer." In 1914, Walker pitched for the Pittsburgh Rebels of the Federal League. He appeared in 35 games for the Rebels in 1914, pitching a career-high 169 1/3 innings with a record of 4–16 and a 4.33 earned run average. He ranked ninth in the Federal League with 16 losses in 1914 and led the league with 12 wild pitches. During the fall of 1914, Walker served as an assistant football coach under Bob Folwell at Washington & Jefferson College. In 1915, Walker played his final season of professional baseball with the Brooklyn Tip-Tops of the Federal League. He appeared in 13 games for the Tip-Tops in 1915, pitching 65 2/3 innings with a 3.70 earned run average. He appeared in his final Major League game on September 29. In 1916, Walker played minor league baseball, playing for teams in Albany and Utica, New York. In the fall of 1916, Walker returned to the University of Chicago as an assistant football coach under head coach Stagg. 1917–1925 Walker served as an assistant baseball coach in the spring of 1917 back at the University of Chicago. During the summer of 1917, Walker played minor league baseball for New Haven in the Eastern League. In September 1917, the Williams College athletic council announced the hiring of Walker as the college's football coach. Walker served as the head football coach at Williams College in 1917 and led the team to the first undefeated season in the school's history with seven wins and one tie. The 1917 Williams team defeated traditional football power Cornell 14–10 in the second game of the season and finished the season with a 20–0 win over rival, Amherst College. In December 1917, Walker was hired by Dartmouth College as the school's head basketball coach. After the