Complex sentence: In 1912, O'Day agreed to become the manager of the Cincinnati Reds, a move that came out of nowhere in the baseball world, as he had not been mentioned as a possibility to take the job.
Split into simpler sentences: In 1912, O'Day agreed to become the manager of the Cincinnati Reds. This move surprised the baseball world, as O'Dayhad not been mentioned as a possibility to take the job.