Grey Comet, a multiple stakes-winning homebred of Star Track Farms who was to attempt a sweep of the New York Stallion Series Sunday, was euthanized Wednesday afternoon in New Jersey.Grey Comet had to be put down because of a slab fracture to the third carpal bone in his right front leg suffered during a seven-furlong breeze at Aqueduct. The injury occured while the New York-bred son of Distinctive Pro was galloping out. He managed to remain on his feet and did not throw the rider, but the injury proved fatal, trainer Gary Contessa said. He was sent to Dr. Scott Palmer in New Jersey where the decision was made to euthanize Grey Comet."The third carpal had been displaced. It was in so many pieces there was just no way to put it back together," Contessa said. Grey Comet was training for Sunday's $250,000 Cab Calloway Stakes. If he had won, Grey Comet would have earned an additional $100,000 bonus for sweeping all three legs of the New York Stallion Series. Previously, Grey Comet won the Great White Way Stakes as a 2-year-old in November and the April 27 Times Square Stakes, both at Aqueduct."Now we will just have to regroup," Contessa said. "You have to have a strong stomach to stay in this game. He was very sound and we were looking forward to going into the stake Sunday as the 1-5 favorite."Grey Comet had proven just as tough against open company during his abbreviated career, as evidenced by his win in the Count Fleet Stakes in his seasonal bow Jan 4. Overall, Grey Comet won five of eight starts with two seconds, including the Gotham Stakes (gr. III), and one third. He earned $355,455 for owners Peter and Marshall Winston.