"[5] During the 1995 season, Janzen was considered one of the best prospects in the Yankees' system and was the centerpiece of a trade deadline deal to the Toronto Blue Jays for reigning American League Cy Young Award winner David Cone.

[7][8][9][10] Janzen made his Major League debut with the Blue Jays on May 12 of the following season, pitching three scoreless innings in relief of Tony Castillo and picking up the win at the SkyDome against the Boston Red Sox.

[3][11] Janzen made the first start of his Major League career on May 27 against the Chicago White Sox.

[3] After the 1997 season, Janzen was selected by the Arizona Diamondbacks from the Blue Jays in the 1997 MLB expansion draft.

Before the start of the 1998 season, he was traded by the Diamondbacks with Todd Erdos to the Yankees for Andy Fox.