Besides being seen on a new network this year, the Breeders' Cup World Championships will have a different sound as well. For the first time since the event's inception in 1984, Tom Durkin will not be calling the Breeders' Cup races for television viewers.Durkin, the voice of the New York Racing Association, signed an exclusive agreement with NBC Sports in February 2006. As part of that contract, he will continue to call the Kentucky Derby (gr. I) and Preakness Stakes (gr. I) on that network. But with the Breeders' Cup shifting from NBC to ESPN this year, Durkin will be on the sidelines for racing's biggest day. A source close to the Breeders' Cup said that Trevor Denman, the voice of Santa Anita Park and Del Mar in Southern California, was ESPN's first choice to replace Durkin. Denman, a native of South Africa, has served as an analyst on NBC's previous Breeders' Cup telecasts.This year's Breeders' Cup will be held Nov. 4 at Churchill Downs in Louisville, Ky."I signed the exclusive agreement, and you can't have it both ways," Durkin said Sept. 2 from his perch high above Saratoga Race Course. "I am very happy with the contract I signed. I feel fine about it. Twenty-two years is a good run to hold a job. This is not a sad or bad feeling, and I'm not the weepy type, anyway. I will call 42 grade I races next year, so I'm not wanting for good horses. There's nothing negative about this at all."It's been an honor and a privilege to have called the Breeders' Cup since its inception in 1984, a memorable, thrilling, and fulfilling 22 years. I hope in some small way I've made those races memorable for racing fans."Durkin, as the on-site announcer at Belmont Park, received a waiver to call this year's Belmont Stakes (gr. I) on ABC as long as he did not appear on camera or be identified as an ABC employee.