The on-loan Wolverhampton Wanderers striker was sent on after 85 minutes with Rovers chasing the game since the 70th when they fell 2-1 down to their hosts.
Explaining why Ennis was not introduced sooner for his first minutes since suffering a hamstring injury six weeks ago, Moore says it would have been a risk.
“I couldn’t bring him on earlier,” Moore said. “He was having no more than ten or 15 minutes today having just come back in.
“He needs the volume in him so we couldn’t pull him on for any longer.
“Though he was there and you want to put him on for the last half an hour, you just can’t do it on a cold afternoon.
“He’ll have a week’s training and he’ll be ready for Accrington.”