"We had 20 attempts at goal, 10 corners. We've got to do better," Lennon told the Irish Examiner. "We keep flashing balls in the box and I always see an opposition defender getting there first, that's something we need to do better. We need to be braver in the final third.
"It's a concern. You keep giving teams encouragement. Dundee United scored a very good goal but didn't create much else.
"The goal gave them something to hang on to, but the amount of chances going begging was frustrating."
Celtic are currently five points clear at the top of the Scottish Premiership.