Matt Gill called on his Under-23s to meet their individual standards in every match, in the wake of their 1-0 victory over Bury in the Premier League Cup.
Owen Wallis's late goal helped City earn a hard-fought win but Gill admitted post-match that he was disappointed with his side's overall performance levels.
"I'm disappointed performance-wise because we've set some good standards this season and especially over the last few weeks with one of our best performances against West Brom," he said.
"I know personnel had changed today and circumstances are slightly different with the FA Youth Cup game tomorrow but I said to the boys: they need to have their individual standards regardless of what position they're playing in or who they're playing with.
"They have lots to think about from today. I'm ultimately pleased to get the win and continue a good run of late but when we look at individual performances, I'm slightly disappointed.
"We need to pick ourselves and make sure we're ready to go again on Friday."
However, Gill was pleased with how his players coped in torrid snowy conditions at Colney.
"The conditions weren't ideal today and I said to the boys that they aren't going to play in perfect conditions all the time.
"It's about who wants to run, tackle, regain possession quicker. We probably didn't sprint enough first half but ultimately the boys dug out the win and it keeps us alive in the competition."