Having burst onto the scene with 19 goals on his debut season last year, the striker has managed just nine league goals this time round - but Lambert insists he has never lost faith in the Belgian striker.
"Christian is only a few goals behind last year," Lambert said ahead of Saturday's Sky Live visit of Chelsea.
"He's not behind that tally by many but everyone thinks he's off, or out of sorts or not the same player. But his goal return is pretty decent because he missed a good month for us earlier this season.
"If he keeps the form he showed in the last game against Norwich then he'll certainly be a handful. I don't need to motivate him or talk about 'second-season syndrome'.
"We've spoken and he knows the situation. He's not naive at all, he knows exactly what's required and what he can do. His ability is there and it always has been.
"He went away with the national team and that breaks up his week from here so I think he'll be in pretty good condition at the moment.
"The two goals against Norwich should certainly give him more of that confidence to go and do it against Chelsea.
"He's up against two centre-halves who are playing really, really well but he did it at Stamford Bridge as well, so he knows he can do it. If him, Gabby (Agbonlahor) and Andi (Weimann) can keep their form then we'll give it a go."
Don't forget you can watch Aston Villa entertain Chelsea on Sky Sports 1 at 17.30 on Saturday, 15 March