Dier conceded that his side's performance was "erratic" but insists that they can still progress when they welcome Gent to Wembley for the second leg next week.
"We did show more aggression than Saturday against Liverpool. I don't think we created enough chances to win," he told BT Sport.
"In the first half, they were the better of the two sides but after half time we were better until the goal. It stopped us in our tracks. We could not get going again. They sat back and we could not get the away goal.
"When you go a goal down, you want to give everything to get back into the game. Maybe we were erratic at times and could have been a bit calmer and waited for our chance. That is something for us to work on. I don't see why we cannot turn it around. This team gave everything against us, we did that but lacked a bit of quality. At home we will be better."
Spurs have now lost four and won just two of their seven European outings this season.