Lambert was the only boss prepared to take a risk on Benteke, 22, when he signed him from FC Genk on deadline day for £7million.
Weimann said: "You can say they missed out because Christian's been brilliant for us this season. He looks scary. But his English is not the best at the moment and he just walks around the place smiling.
"He's a nice guy and seems like a gentle giant, but I've not seen him angry yet - maybe you wouldn't want to!
"If he keeps playing like this, I'm sure defenders will be looking at him. But he's a big presence, so it's hard to miss him."