Norwich 1-4 Villa boss verdict: Lambert hails Weimann
Lambert opted to rest Weimann for Villa's previous two matches but the decision to bring him on for the injured Darren Bent paid dividends at Carrow Road.
Two second-half strikes from the Austrian pushed Villa towards the semi-finals and Lambert was quick to praise his incredible hunger for the game.
"He was brilliant," said the Villa boss. "One thing about Andi is he is a natural finisher and his work ethic for the game of football is absolutely brilliant.
"If Andi was getting X amount of money, you'd get the same out of him in every game.
"That is a testament to him. I left him out just to give him a rest in the last couple of weeks but Weimann is a natural goalscorer.
"He ran himself into the ground, especially in the two Manchester games and the Arsenal game, but he came back tonight and he certainly knows where the goal is."
Lambert felt the 4-1 victory was a fitting reward for some encouraging performances over the past six weeks.
He was also thrilled for the "ferocious" claret and blue faithful who descended on East Anglia in their droves to help roar Villa into the last four.
"I thought in the whole game we were excellent," he added.
"Their goalkeeper made some terrific saves. Norwich had chances as well.
"But I thought the lads were excellent. We've been playing like that since the Sunderland game.
"We've been playing really, really well and not had the results we might have had. I'm delighted for the team, I really am.
"A massive thanks to the Villa fans too. I thought tonight they were unbelievable - they did ferociously well in their support.
"It was a three-hour journey to come down and I thought they were absolutely fantastic for us."
The only disappointing note for Villa was the first-half injury to Bent, who left the field with a hamstring problem.
Lambert had been pleased with the England striker's efforts up until his departure.
"I thought Darren was looking pretty sharp," the manager added.
"It was just a blow for us. I don't know how bad it is but he was hurt. It is just a thing we have to contend with next week."
Make sure you back the boys against Tottenham.