Born in Bloomingdale, Michigan, Killefer attended the University of Michigan from 1904 to 1907 before joining the Detroit Tigers in September 1907. Killefer led the American League and the National League in being hit by pitches in 1910 (16) and 1915 (19). Killefer batted .248 with 3 home runs in 467 career games. Though he played on the Tigers' American League pennant winning teams in 1907 and 1908, Killefer did not play in either World Series. On August 13, 1909, the Tigers traded Killefer and Germany Schaefer to the Washington Senators for Jim Delahanty.
Red with the Pacific Coast League.
On July 20, 1916, Killefer was traded by the Reds with Buck Herzog to the New York Giants for three future Hall of Famers: Christy Mathewson, Edd Roush, and Bill McKechnie. After the trade, Killefer had only one at bat for the Giants before retiring.
In 467 major league games, Killefer was a versatile player who logged time at every position except pitcher: 135 games as a center fielder, 135 games as a left fielder, 129 games as a second baseman, 27 games as a right fielder, 11 games as a third baseman, 8 games as a shortstop, 3 games as a catcher, and 2 games as a first baseman.
Killefer is noted as being the first ever batter in a National League game at Wrigley Field (Wrigley had been a Federal League park in its first two years), as a visiting team batter for the Cincinnati Reds.
After his playing career ended, Killefer was a minor league manager for 25 years, (1917–1941). His managerial career included stints with the following teams:
Los Angeles Angels in the Pacific Coast League (1917–1922). He led the Angels to second-place finishes in his first three years with the team and finally to a PCL championship in 1921.
