A second post-race drug test for Kentucky Derby winner Medina Spirit confirmed a prohibited substance was present, a lawyer for the horse’s trainer said on Wednesday, raising the possibility the dark bay colt might be disqualified. While a decision on whether to disqualify Medina Spirit will depend on the outcome of a Kentucky Horse Racing Commission investigation, Churchill Downs Incorporated (CDI) moved swiftly by banning the colt’s Hall of Fame trainer Bob Baffert for two years. In making the ruling, CDI said it could no longer overlook Baffert’s history of drug testing failures. In just over a year, five Baffert trained horses have failed drug tests. “Mr. Baffert’s record of testing failures threatens public confidence in thoroughbred racing and the reputation of the Kentucky Derby,” said Bill Carstanjen, CEO of CDI in a statement. “Given these repeated failures over the last year, including the increasingly extraordinary explanations, we firmly believe …