Brentford boss Andy Scott was critical of his side despite the 2-1 Carling Cup win over Cheltenham.
First-half goals from new boys Robbie Simpson and Craig Woodman gave the hosts the lead before Shaun Jeffers reduced the arrears on the hour mark.
Victory ensured Brentford bounced back from their opening-day defeat at Carlisle but Scott feels his side have a lot of improving to do.
"We needed a win after losing on Saturday so the result and getting into the next round were important," he said.
"But it was very frustrating - in the first half we were fine doing what we are best at and what we are good at, but for some reason after the break they stopped doing the things that had given them the lead.
"Only they could tell you why they stopped doing what they have been doing in training, but we will keep working hard to make sure the good things run into games for the whole 90 minutes."