Complex sentence: However, the Cubs hopes for winning a World Series title were cut short during the 2003 National League Championship Series against the Florida Marlins, who would go on to claim the 2003 World Series.
Split into simpler sentences: However, the Cubs hopes for winning a World Series title were cut short during the 2003 National League Championship Series against the Florida Marlins. The Marlins would go on to claim the 2003 World Series.