Marple said that like a top athlete, Great Day Rising "left it all in the ring.
"He got a little focused on the carnival before the class, and he had to work a little harder," Marple said.
His horse may work again Saturday night
The horse may work again in Saturday night's amateur five-gaited championship, depending on the evaluation of his trainer, Mike McIntosh of Westfield, Ind., and perhaps on Saturday's weather forecast.
Marple said he'll return to Harrodsburg for the Saturday night class if he and McIntosh decide to enter the horse, but today he was scheduled to be on a plane back to Dallas, where he works as a lawyer.
Great Day Rising already has wins this year in shows at River Ridge and Indianapolis, and he most recently took second place in his class two weeks ago at Lexington.
Marple is pointing toward next month's World's Championship Horse Show in Louisville, and he said he wants his horse to face the best competition possible along the way.
"Harrodsburg was the best show we could find," Marple said. "We go to the competition."
But Marple said his trips to Harrodsburg - this is the fourth time he has shown here in the last six years - are also something of a trip back in time.
Some of Marple's roots lie not far from the Mercer ring, and he said that made his victory there even more special.
"It's real special," he said. "We just love this town. It's like going back in time a little bit, it's so refreshing."
Marple's father, Earl Marple, was born in Springfield and rode saddlebred horses from his youth. In fact, Marple said at age 17, his father rode a saddlebred from Springfield to Indianapolis when his family moved there.
Great Day Rising came from Shatner's farm
Marple returned to Springfield last year to buy Great Day Rising at Kalarama Farm. He had high hopes for the horse, which was bred by William Shatner at Shatner's farm near Versailles and won a 3-year-old championship.
Marple bought the horse just before last year's Harrodsburg show and won a third-place ribbon here.
"We did pretty well and we found out what we had," he said.
Marple didn't wear spurs in the ring Wednesday, and he carried no whip. He said that's common practice, and he makes sure the trainers he works with know it.
"All our horses are pets in every sense of the word," he said. "We treat them with kindness."
Marple said Great Day Rising has been kind to him so far, and he looks forward to what the future holds with this horse.
"He's the best horse I've ever had or will ever have," Marple said.