Westwood was signed during the final week of the summer transfer window from Crewe and was not chosen in Lambert's line-up during the early part of the season.
But the 22-year-old has looked at home since making his full debut at Sunderland last month and has impressed when starting the last six matches during Villa's mini revival.
Another youngster, 21-year-old striker Christian Benteke, has grabbed most of the headlines but Westwood's contribution has also impressed Lambert.
The Villa manager said: "I think a lot gets overlooked with Ashley but he has just come in here and has taken to it no problem whatsoever.
"He was captain at Crewe and played a lot of games in men's football before he came here so he knew what it was about.
"I trust people to go and play, to go and give everything they've got and he has not let me down.
"If you look at the stats regarding his passing, they are terrific, something like a 91% success rate and he never gives the ball away. He's been exceptional."