The Australian international joined Villa on a free transfer from AZ Alkmaar in the summer in a deal that was concluded by Alex McLeish before he was sacked by the Villa Park hierarchy.
"Brett has done great; he's got energy to burn. I'm really happy with the way he's playing," said Lambert. "He's been brilliant, he's a top lad as well, he'll definitely do well. If he keeps going the way he's going he'll have a really good season.
"He's got a great desire for the game, a great enthusiasm for the game which is important. I don't know if he had offers from the Premier League before, he might have done. Maybe teams did go in for him, I'm not so sure. But Villa are fortunate to have him,
"If Alex McLeish scouted him then it's great credit to him because he's doing great for the club."
The 28-year-old has yet to score a competitive goal for Villa.