Holmes, 18, made his first team debut as a 49th minute substitute during the 1-0 third-round loss at the KC Stadium.
There were full debuts for striker Danny Carr and defender Tommy Smith as Robins, mindful of Friday's Championship fixture with Blackpool, made 10 changes to his starting line up.
"I was pleased with a number of our younger lads, and Duane in particular," said Robins.
"He showed the kind of bright spark I was looking for and carved out a few opportunities for himself.
"Danny Carr also did that in the first half and Tommy Smith put in a strong performance and gained some vital experience.
"But as a team, I thought we played within ourselves, and we needed to show more bravery. But it's a learning curve, and we need to give players on the periphery opportunities like this."
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