ハワイ・ウィンターリーグ
Jansen was signed as an undrafted free agent catcher by the Dodgers organization on November 17, 2004, and was assigned to the Rookie Class Gulf Coast Dodgers, where he played in 37 games and hit .304 before being promoted to the Ogden Raptors of the Pioneer League on August 26. He had two hits in 11 at-bats in three games for Ogden. He was back with the Gulf Coast team the following season, hitting .245 in 35 games. After the season he played for the North Shore Honu in the Hawaii Winter Baseball League, where he hit .121 in nine games.