A veteran of 55 years in professional baseball, Nixon managed at virtually every level of the sport, from the lowest minor league to MLB assignments with the Cincinnati Reds and Atlanta Braves.

At the close of spring training in 1966, Boston packaged him and second baseman Chuck Schilling in a trade with the Minnesota Twins for left-handed pitcher Dick Stigman.

Beginning the year at Double-A Pittsfield, he was recalled in July and in his first at bat, he hit a three-run, pinch-hit double, providing the winning margin in a 6–5 victory over the Twins.

After compiling the best overall record in the National League West Division during the strike-affected split season of 1981, the Reds unraveled in 1982, plummeting into last place and losing 101 games.

Nixon worked for Chuck Tanner in 1986–87 before his appointment as pilot of the Greenville Braves, the club's Double-A Southern League affiliate, for 1988.

While new general manager Bobby Cox had done much to rebuild the Braves' farm system, at the National League level they were in the midst of their worst stretch since their days in Boston.

When the Braves dropped 27 of their first 39 games in 1988, Nixon was recalled from Greenville to succeed Tanner on May 23—a rare promotion of a manager from AA all the way to the majors.

Nixon remained in the game as a minor-league manager and instructor, except for 1992, when he returned to the American League to spend one year as a coach for the Seattle Mariners.

In 2008, Nixon, then 73, was still active in baseball as a roving instructor in the Texas Rangers' farm system, appointed by the club president at the time, Nolan Ryan.