The Holland international has one year remaining on his contract and his impressive performances in the World Cup have led to speculation over a move away from Villa Park.
Southampton are among the clubs linked with the 29-year-old, who was given an extended break following his run to the semi-finals in Brazil.
Vlaar returned to the fold on Saturday but was restricted to the role of a spectator for the club's 4-1 pre-season friendly defeat at Groningen.
With less than two weeks until Villa's opening game of the season against Stoke, Lambert said: "Ron has told me he is concentrating on that game. He's not had much of a break, but he's enthusiastic, positive and raring to go.
"It was a good feeling I got from him. To be fair, it was a really brief conversation I had before the game as I was preparing the lads for the match.
"Ron's got another year still to go on his contract, it's not as if he's at the end of it.
"Once we get back I'll sit with him, we'll have a bit more time, but he loves it at Villa, that's well known."
Experienced goalkeeper Shay Given has also urged the club to do all they can to keep hold of the Dutch international.
The 38-year old told Sky Sports News: “I think there are a few players who are in for negotiations for new contracts at the minute. I’m sure the club are working hard behind the scenes to sort that out.
“Ron had a fantastic World Cup of course, he’s our captain as well and we all want him to stay.”