Goals from Papiss Cisse and a Yohan Cabaye wonder-goal condemned Villa to their fourth home league defeat in a row, leaving them languishing in the bottom three.
However, Christian Benteke's second-half penalty seemed to revive the home side and they missed several chances to equalise late on, with Lambert keen to focus on that fightback.
"I have never seen a standing ovation after a game in which we have been beaten, but it shows you the effort." he said.
"We never played well in the first half, but I couldn't fault the players in the second half. We changed it around. Some people can hide behind tactics, but the game is about players.
"The first goal was really poor. But second half we looked like we could pull it back. The response gives us hope, because it's in our capabilities to go and do that. Credit to them [his Villa players] in the second half. They came out and they were relentless, but it was too little too late."
The former Norwich boss hinted that he may be able to bolster his squad before the end of the transfer window, but refused to reveal any names.
"Money dictates and the situation hasn't changed in the last month. I don't know. I'll just see what the next two days bring," he added.