Complex sentence: Slowey ascended rapidly through the Twins minor league system and after failing to make the team as a dark horse candidate out of spring training, he began the 2007 season with the AAA Rochester Red Wings.
Split into simpler sentences: Slowey ascended rapidly through the Twins minor league system and after failing to make the team as a dark horse candidate out of spring training. He began the 2007 season with the AAA Rochester Red Wings.