NEW YORK—Brad Cox insisted he wasn’t sitting around waiting or worrying about whether a disqualification of Bob Baffert’s Kentucky Derby winner would give him his first victory in a Triple Crown race. Essential Quality captured the Belmont Stakes on Saturday to make sure Cox wouldn’t need to wait a second longer to be a Triple Crown race-winning trainer. The striking gray colt who was bet down 6–5 as the favorite passed early leader Hot Rod Charlie around the final turn and charged ahead to the wire to win the 1 1/2-mile $1 million race in front of 11,238 mostly maskless fans at Belmont Park. Cox could be a Derby champion with Mandaloun if Baffert-trained Medina Spirit is disqualified for failing a postrace drug test. Two samples have confirmed the presence of the steroid betamethasone, though Kentucky officials have not yet announced the horse’s disqualification—a move that would elevate Mandaloun to …