Mike Pegram's Danthebluegrassman, a surprise entry when post positions were drawn Wednesday, was scratched from the 128th Kentucky Derby early Saturday morning after he "tied up" following a routine gallop at Churchill Downs.Trainer Bob Baffert said the son of Pioneering "galloped well and was full of himself when he walked off the track." After the colt was bathed, it was noticed that he was "walking short" in his behind, a result of tying up. Baffert said the condition is comparable to a nervous reaction. "It's like getting cramps in your back," baffert said. "The muscles in your back get tight and if you do something with them, they can tear."Dr. Doug Berry treated the colt immediately, administering muscle relaxers. "If you don't get on it right away, it could injure him," Baffert said. "He could tear a muscle in his back. We had to give him some muscle relaxers and you can't run a horse after you give them all that.""The horse is okay," Baffert said. "He's done this before, but not for a long time. It is tough on his connections. (Owner) Mike (Pegram) took it well, but it was just not meant to be."More than Pegram, Baffert said the defection of Danthebluegrassman will be felt more by Dan Chandler, the colt's namesake who brought about 50 friends and relatives to the Derby.Installed at 50-1 morning line odds after finishing last in the Santa Anita Derby, Danthebluegrassman was at 24-1 odds at the close of Friday's advance wagering.