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 main role was help facilitate the Bulls stars and score when needed, but he also brought one 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 didn't, he would not have been kept), and Kerr helped Chicago win the next three NBA Championships (1996-98).  Kerr was first in 1995/96 in the NBA 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 smart, Kerr was traded to San Antonio, where he provided a similar role in two Spurs Championships. He later became the Head Coach of Golden State, where he helmed them to three titles.  

So yes, talk about a winner!