LOUISVILLE, Ky. — Always Dreaming splashed through the slop to win the Kentucky Derby by 2 3/4 lengths on Saturday, giving trainer Todd Pletcher and jockey John Velazquez their second victories in the race but their first together. Pletcher and Velazquez have teamed up often over the years and are the sport’s leading money winners. On their own, they were a combined 2 for 63 coming into America’s greatest race.