After five years in the NBA (playing for Phoenix, Cleveland, and Orlando), Steve Kerr was signed by the Chicago Bulls in 1993 to be a backup Point Guard.  Most people (including Chicago fans) probably didn't pay it much attention.  They certainly did when he left.

Kerr played five seasons with Chicago, and he never started a game, but he also averaged 23.2 Minutes per Game and found himself to be a key contributor in the Bulls offense.  Kerr's primary role was to help facilitate the Bulls' stars and score when needed, but he also brought one of the lowest turnover rates in basketball.  

Michael Jordan was in his baseball sabbatical when Kerr was signed, and when he returned late in the 1994/95 season, he inherited Kerr, who finished the year first in Three-Point Field Goal Percentage.  Jordan took to Kerr (if he hadn't, he wouldn't have been kept), and Kerr helped Chicago win the next three NBA Championships (1996-98).  Kerr was first in the NBA in 1995/96 with the lowest Turnover Percentage, and in the 1997 Finals, it was Kerr (taking a pass from Jordan) who sank the winning shot.

Efficient and intelligent, Kerr was traded to San Antonio, where he served in a similar role during the Spurs' two championship seasons. He later became the Head Coach of the Golden State Warriors, leading them to multiple titles.  

So yes, talk about a winner!