Charlie Austin struck once in both halves to condemn Villa to their fifth successive Premier League defeat, despite winning three of their first four games.
Lambert's side boasted more shots and ended the contest with 65% in the possession stakes, and the Scot says that deficiencies at both ends undermined his team's effort.
"I think that is the most we have had of the ball, possession-wise, but that is why I'm never one for stats. The main stat is putting the ball in the net and keeping it out," he told Sky Sports News.
"I thought we defended poorly for the two goals. We have got to be more clinical in the last third of the pitch but the two goals are disappointing because we had most of the ball."
Villa will look to end their five-game losing streak when they welcome Tottenham Hotspur to the West Midlands on Sunday.