Highly touted in college, Bannister was the Phillies' first-round pick in the 1973 draft. Although versatile (he played every position but pitcher and catcher) he never lived up to his college raves and was rarely a regular. Only once, as the 1977 White Sox' shortstop, did he play in over 100 games at a position, and then he led all AL shortstops in errors (40). He led the American League in sacrifice flies (11) in 1977.
In 12 major league seasons he played in 972 games and recorded 3,007 at bats, 430 runs, 811 hits, 143 doubles, 28 triples, 19 home runs, 288 RBI, 108 stolen bases, 292 walks, with a .270 batting average, .334 on-base percentage and a .355 slugging percentage.
In July 1972, as an amateur, Bannister accidentally killed an opposing player during a game. Bannister was a participant in a Baseball Federation tour of Japan, and while attempting to complete a double play during a game against a Japanese team, he made a throw to first base which struck the head of Akira Toumon advancing from first base to second base. Toumon was knocked unconscious, and he later died at the hospital as a result of cerebral contusion.