Complex sentence: Red Bull Arena, the new home of the New York Red Bulls opened for the start of the 2010 season, and the Philadelphia Union opened PPL Park, midway through their inaugural season, in June 2010.
Split into simpler sentences: Red Bull Arena, the new home of the New York Red Bulls opened for the start of the 2010 season. The Philadelphia Union opened PPL Park, midway through their inaugural season, in June 2010.