"Symington has no fear and you expect the unexpected with him," said Abbot. "But he will learn to get more consistent and he's shown that he can come on and make an impact.
"Beck made a significant contribution and David was a real handful with his power and pace and he has unbelievable shooting power.
"With our guts and determination we probably deserved to come out winners. Sometimes the fans have got to be a bit patient. As these youngsters get older they will get more consistency."
The win saw Carlisle reach the third round of the League Cup for the first time since 2009.