Lambert said: "I can understand why people are comparing with Drogba with the size of the two guys - but Christian is his own man.
"It's unfair for me to turn around and say he's going to be the next Didier Drogba with the career he's had.
"Christian has only just turned 22. But the potential there is incredible, what he can achieve.
"He's been absolutely brilliant for me, not just as a footballer but as a guy he is really humble, which is important. He's been brilliant."