Complex sentence: On Opening Day 2015 the Pirates' loss to the Cincinnati Reds represented its 10,000th franchise loss since moving to the NL and making it the fourth MLB team to achieve this distinction, after the Philadelphia Phillies, the Atlanta Braves, and the Chicago Cubs.
Split into simpler sentences: On Opening Day 2015 the Pirates' loss to the Cincinnati Reds represented its 10,000th franchise loss since moving to the NL. This made the Pirates the fourth MLB team to achieve this distinction, following the Philadelphia Phillies, Atlanta Braves, and Chicago Cubs.