However, Lambert is keen to keep his feet on the ground and insists that they won't get carried away as they still face a battle against relegation.
"I think it's our best performance of the season. I thought we were absolutely superb," said the striker.
"We got the early goal that we needed and just got stronger and stronger. We realise the position we are in, but we believe we are good enough to stay in this division and then push on.
"We want to open up the gap on the bottom as quickly as possible."
The result is just the 13th time in Premier League history that the reigning champions have been beaten by a newly-promoted team.