Complex sentence: The Yankees and the Red Sox finished both tied for first in, when the Yankees won a high-profile Pennant playoff for the division title, after the Red Sox lost a 14-game lead over the Yankees more than halfway through the season.
Split into simpler sentences: The Yankees and the Red Sox finished tied for first in; subsequently, the Yankees won a high-profile Pennant playoff for the division title. The first--place tie came after the Red Sox had enjoyed a 14-game lead over the Yankees more than halfway through the season.