On Sunday, Casse could only look on in disbelief as his prized horse Danzig Moon was involved in a fatal accident during the $150,000 Plate Trial at Woodbine Racetrack. The 2-1 race favourite, arguably the highest-profile horse at Woodbine, was standing second to leader Midnight Trace in mid-backstretch before he suffered a compound fracture in his right hind leg and was euthanized.
"It's been tough on me, very tough on Mr. Oxley (owner John C. Oxley) and especially crushing to Norman (assistant trainer Norman Casse, Mark's son)," a sombre Casse said Tuesday afternoon. "The biggest problem is this, you don't know why it happened.
"If you knew why it happened you could try to do it better or do it differently. So now we've got this fear and worry that it could happen again. It's going to take a long time to be able to watch races because they (horses) are part of your family. We had the (Woodbine) Oaks the next race (Sunday), we had four horses in it and I couldn't even watch."
Later on Sunday, Norman Casse tweeted a photo of himself posing with Danzig Moon and the message, "Overwhelmed by everyone's support. Danzig Moon is a horse/friend I will never forget. Today is a very hard day."
The three-year-old colt was making his first start since finishing sixth at the Preakness Stakes on May 16. Earlier, Danzig Moon was a solid fifth in the Kentucky Derby, the first jewel of American thoroughbred racing's Triple Crown.
"He took us to the Derby and ran very well there," Casse said. "You never get used to it, you just never do.
"We're dealing with athletes that run very fast. Their bone is actually not as big as ours but they run 40 miles an hour and weigh 1,000 pounds. Unfortunately things happen."
A win Sunday would've established Danzig Moon as the favourite for the $1-million Queen's Plate on July 5, the first race of the Canadian Triple Crown. Casse, six times Canada's top trainer, earned his first Plate victory last year with champion filly Lexie Lou.
"We said from the beginning, even when we were making our Derby and Preakness plans, the Queen's Plate was really important to us and Mr. Oxley," Casse said. "The only way he wasn't going to go to the Queen's Plate was if he had performed poorly in the Plate Trial.
"Then I would've saved him for the Prince of Wales (second race of Canadian Triple crown at Fort Erie Racetrack)."
Moments after Danzig Moon broke his leg, R U Watchingbud, with Emma-Jayne Wilson aboard, ran into the race favourite from behind. Fortunately, Wilson, R U Watchingbud and Julien Leparoux, Danzig Moon's jockey, were all unhurt.
"Julien was lucky, very lucky, but was obviously shook up because he also had a relationship with the horse and that was difficult," Casse said. "People don't realize just how much horses mean to the people that take care of them.
"They have a great love for them and I feel terrible, terrible for the men and women who were so close to him."
Sunday's accident only further deepened Casse's respect and admiration for jockeys and the risks they willingly assume.
"Their job every day is so dangerous," he said. "I said to Julien, 'I can't even stand to watch a race, I can only imagine what it must be (like) to have to ride the next one?"
Casse has watched the Plate Trial replay "five or six times," but can't bring himself to re-live Danzig Moon's accident.
"No. I won't, I just can't," he said. "When we got to the point where I knew it was going to happen I just turned away."
While admitting Danzig Moon could be a handful at times, Casse there was no questioning the strapping three-year-old's passion to race.
"He was tough," Casse said. "They called him the bad boy because if you weren't watching he'd bite you . . . that was his sport.
"But I have to tell you he loved to train and when it was race day he was focused. He'd bite you and try to get you at the barn but when he went on to the racetrack it was business and he loved to do it. He was such a good horse."
Danzig Moon earned $311,120 with a win and two second-place finishes in seven lifetime starts.