John A. “Jack” Zduriencik ( /zɜrˈɛnsɪk/; born January 11, 1951 in New Castle, PA) is the General Manager of Major League Baseball's Seattle Mariners.

Jack Zduriencik began his career in professional baseball as a second baseman in the Chicago White Sox farm system. From 1973 to 1974, he spent time playing for both the Gulf Coast White Sox and the Appleton Foxes.

Following his playing career, Jack spent several years as a coach for both baseball and football. His coaching tour included stops at Austin Peay State University (1975–77), Clairton High School (PA, 1977–80), and Tarpon Springs High School (FL, 1980–82).

Zduriencik returned to professional baseball in 1983. Successive roles involving scouting and player development comprised most of the next two-plus decades of his experience, as he spent time in the positions of:

Zduriencik was so successful in Milwaukee that many observers^[who?] felt that he deserved a large part of the credit for the Brewers' eventual return to playoff contention in 2008. Brewers General Manager Doug Melvin praised Zduriencik's efforts when he was quoted as saying: