The Austrian forward grabbed a goal and an assist in the crucial win over Villa's relegation rivals and Lambert was delighted with Weimann's contribution at Villa Park.
"I don't think he was a regular in the side but we gave him a chance and he is playing exceptionally well," Lambert said. "I know his natural position is probably through the middle but that's difficult with the way Christian Benteke and Gabby Agbonlahor are performing. But, whether or not he has to play off the line, he seems to score goals.
"The biggest compliment I can pay him is that he is a brilliant guy who gives you everything and that can take you a long way.
"It was a brilliant goal that he scored and, for the third goal, he just never gave up the ghost. He's a phenomenal lad to work with."
Defender Ron Vlaar was also quick to heap the praise on Weimann and the Villa captain hopes the club can convince the 21-year-old forward to sign a new deal at Villa Park.
Vlaar told reporters: "He scores a lot of goals and he's always in the right spot at the right time. I heard [he and the club] are talking to each other, but of course it's very important that he stays playing for Aston Villa."