Tonev has struggled to make an impact on his first season in the Premier League with only six starts for Villa, and his manager has challenged him to raise his game.
The 24-year-old last started a league game in December, and has only featured once in 2014 - as a substitute against Everton last month.
Lambert is confident Tonev has the qualities to be a success at Villa Park, but wants him to start showing them if he wants to play a part in their remaining 10 matches.
"You are looking for more from Aleks," the Scot told the club's official website. "He has the attributes – speed, skill and two feet.
"Everything is there for him. It's just taking him longer to adjust with a lot of things.
"He has all the things there, it's just about getting them together."
Tonev, an attacking midfielder, arrived in England having spent two years in Poland with Lech Poznan.
