Egg Head, a 3-year-old rising star on the sprint division scene, was euthanized Monday after succumbing to a case of founder.Trainer Kiaran McLaughlin called the son of Honor Grades "one of the best horses I've ever trained." McLaughlin, speaking from Belmont Park Wednesday, said everything that could have been done to save the colt was. "He was scheduled for a work two weeks ago Sunday," said the conditioner who also owned a part-interest in the dark bay. "We came into the stall and he was lame, left hind, with a blown-up hock--just out of the blue. That's what started the whole thing. "We treated him aggressively but it just went right down hill and he foundered. When one founders there are as many causes as cases and it just progressed to the point where we had to put him down."McLaughlin and a group of several investors purchased a 45% interest in the horse from the colt's main owner, Harvey Clark, after his impressive 9 1/2-length victory at Delaware Park in the "Jock" LaBelle Memorial Stakes May 7."Harvey is just a super owner, and this is a real shame," said McLaughlin. "This was a very, very nice horse. He was one of the best 3-year-olds in the country over a mile--we knew that--and we were going to stretch him out to find out far he could go."I also feel bad for (trainer) Lynda Knee, who had him for most of his career. She did a great job with the horse and I know she had a special relationship with him."The LaBelle win earned Egg Head a Beyer Speed Figure of 112, one of the year's highest postings for a 3-year-old at any distance, and also high on the rankings among all ages up to a mile. He made seven career starts, winning four, and earning $145,420.Egg Head made his first start under McLaughlin's tack in the Riva Ridge Stakes (gr. II) June 11 at Belmont. The race was memorable for featuring an undefeated Lost in the Fog, who was given his stiffest test to date by a game Egg Head who finished just 1 1/4 lengths behind the superstar.