Lambert's men had to dig in a for a point after Joe Bennett was sent off early in the second half for a second bookable offence.
Villa could not hold onto Christian Benteke's first-half goal as Michael Turner's late effort ensured a share of the spoils for Lambert's former club.
"I have probably mixed emotions," said Lambert. "We were one-nil up. I thought it was a brilliant finish from Christian to put us one-up. And then there was the sending off. But the lads showed unbelievable spirit to not get beat, we threw bodies on the line - so mixed emotions."
Lambert admitted he was disappointed by the sending off of Bennett following a tangle with namesake Elliott.
"I initially thought that Joe Bennett has grabbed Elliott Bennett but when you look at it again they're both at it and Elliott has Joe by the neck initially," added Lambert.
"But the referee calls it. It was disappointing."
Lambert also defended his decision to leave Darren Bent out of his starting line-up with Benteke starting up front alongside Gabriel Agbonlahor, feeling people are reading too much into the situation.
"I just think Christian and Darren are totally different players, they have got their own different attributes," continued Lambert.
"I thought Gabby was excellent today and I had to take him off because of the sending off so Christian was a handful and his goal was a great goal.
"I have to get a team that wins as well and Darren is part of the whole thing as well so there is nothing at all.
"I pick a team that I think can win a game. I think people can make a lot out of things. I have got to pick a team that will win a game."