| Jason Isringhausen | July 31, 1999 | Traded by the New York Mets with Greg McMichael to the Oakland Athletics for Billy Taylor. |
| November 5, 2001 | Granted Free Agency. |
| December 11, 2001 | Signed as a Free Agent with the St. Louis Cardinals. |
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| Billy Koch | December 7, 2001 | Traded by the Toronto Blue Jays to the Oakland Athletics for Eric Hinske and Justin Miller. |
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| Keith Foulke | December 3, 2002 | Traded by the Chicago White Sox with catcher Mark Johnson, minor league pitcher Joe Valentine and cash considerations in exchange for closer Billy Koch and two minor leaguers (December 12, 2003 Chicago White Sox acquired minor league pitcher Neal Cotts and outfielder Daylan Holt from Oakland as players to be named in the Koch-Foulke deal) |
| December 8, 2003 | Keith Foulke Offered arbitration by the Oakland Athletics |
| December 13, 2003 | Boston Red Sox signed free-agent RHP Keith Foulke to a three-year deal that includes a vested option for a fourth year. |
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| Arthur Rhodes | December 22, 2003 | Signed free agent LHP Arthur Rhodes to a three-year contract with the Oakland Athletics |
| Octavio Dotel | June 24, 2004 | The Oakland Athletics acquired RHP Octavio Dotel and cash from the Kansas City Royals in exchange RHP Mike Wood and 3B Mark Teahen. The Royals acquired Dotel from the Houston Astros along with C Jon Buck in exchange for OF Carlos Beltran. |