Complex sentence: Initially Banks'double play partner was Gene Baker, the second black player on the Cubs and Banks' roommate on road trips, thus making Banks and Baker the first all-black double-play combination in major league history.
Split into simpler sentences: Initially Banks'double play partner was Gene Baker, the "second" black player on the Cubs, and Banks' roommate on road trips. Thus making Banks and Baker, the first all black double play combination in major league history.