Complex sentence: The Mets were to have home field advantage for this series, as the Dodgers (the 1985 NL West Champions) had it the previous year, however, a regular season game between the Chicago Bears and Houston Oilers made the Astrodome unavailable for October 12.
Split into simpler sentences: The Mets were to have home field advantage for this series, as the Dodgers (the 1985 NL West Champions) had it the previous year. A regular season game between the Chicago Bears and Houston Oilers made the Astrodome unavailable for October 12.