The 22-year-old old Belgian scored 19 goals in his first season in the Barclays Premier League and has been linked with a move away from Villa Park.
But Lambert, who said talks had already begun over improving Benteke's existing contract which has three years left to run, insisted the player still has plenty more to prove.
Lambert told talkSPORT: "I don't really 100 per cent know what's happened but he's got three years here at Aston Villa and the club have always come first.
"He's had one of those seasons where he's never really been injured and he's never been suspended except the last day.
"It's a unique thing, and he's got to remember that he's only 22 years of age - he's got so much to learn.
"He's only a kid starting out and he's going to have ups and downs like everybody else. Once he starts to play 400 or 500 games you might think, 'yeah, he's right good player'.
"I think sometimes we've got to have a reality check here. This lad's only been in Britain for 10 months. He's got the status at Aston Villa and everybody loves him."