Complex sentence: The 2017 Road to the Kentucky Derby is a series of races through which horses will qualify for the 2017 Kentucky Derby, whose field is limited to 20 horses, with four'also eligibles' in case of a late withdrawal from the field.
Split into simpler sentences: The 2017 Road to the Kentucky Derby is a series of races through which horses will qualify for the 2017 Kentucky Derby. The field for the Derby is limited to 20 horses, with four'also eligibles' in case of a late withdrawal from the field.