His playing career ended in May 1969 when he sustained an Achilles tendon injury as a member of the Angels[2] and began his minor league managing career in 1971.
Cottier was in his third season as the Seattle Mariners' third base coach in 1984 when manager Del Crandall was fired with 27 games left and Cottier was appointed interim manager on September 1.[3][4] He led the team through 1985 and into the first 28 games of 1986. With the M's at 9–19, sixth in the AL West, Cottier was fired on May 8 and succeeded by interim manager Marty Martínez for one game before Dick Williams took over.[5] His career record as a major league manager was 98–119 (.452).[6]