<prompt> Feleletša polelwana e latelago: Jansen o ile a boela Pacific Coast League e le sebapadi-molatedi wa Seattle 1955 le 1957 le Portland 195860. Ka morago ga mogala go tšwa go yo e kilego ya ba sehlopha Alvin Dark, Jansen o ile a boela go Major Leagues bjalo ka pitching mohlahli bakeng sa San Francisco Giants ka, le Dark bjalo ka molaodi. Jansen o ile a dula e le molatedi wa go lahlela ka nako ya ngwaga tše lesome tee, gomme a thuša go hlabolla bokamoso bja Hall-of-Famers Juan Marichal le Gaylord Perry. Nakong ya ge a be a le mošomong, di-Giants di ile tša tšwelela ka 1962 World Series le  <response>: National League Championship Series ya 1971. Ka morago o ile a fetela mošomong wa gagwe wa mafelelo wa go ba molaodi wa MLB, a šoma ka dipitša tša Chicago Cubs ka 73, a šomela molaodi wa gagwe wa kgale wa Giants, Leo Durocher, gomme ka morago a šomela Whitey Lockman yo e bego e le mošomimmogo le yena. 