The Villa striker made a huge impact last season, giving defenders a torrid time with his physique and technical ability as he bagged 19 league goals.
"Looking at him since he's come back from his break and the games he's played he's been excellent," said Lambert.
"He's not lost his goalscoring exploits. To me, Christian is just getting better.
"He's grown in confidence a lot. He's a big, big athlete and a really top footballer.
"I'm not going to put levels of expectancy on him. If he goes out and tries his best and gives it everything he's got then I think that's all you can ever ask of anybody.
"He'll have his own standards and his own heights that he wants to achieve. Looking at him at this moment in time, in pre-season and in training, he's ready for it."
Villa were relegation candidates last season but many fans are talking about a top-10 finish this campaign but Lambert is refusing to get carried away.
"I don't know," he said. "You never can predict anything about what's going to happen next season.
"I certainly hope it won't be as tough as last season.
"You give it a right good go. I'm excited by it, I can't wait to get going.
"We can't start games the way we did at times last year. We've got to be bang at it from that first minute. You don't have time in this league to bed yourself in for 15 minutes or so.
"We have to be ready and I think that's the big thing that we've learned. We have to be right on it straight away."