The Belgium international incurred the problem in Saturday's 1-0 win at Norwich and the original prognosis saw him ruled out for up to six weeks.
But Lambert has issued an upbeat assessment on Benteke's condition and is hopeful he may be back in action for the home game with Everton on 26 October.
"He is doing great. I think he will be back quicker. We'll have to wait and see," said Lambert.
"We've two games before the international break, which has probably come at the right time for him and for us.
"The worst scenario was he was going to be out for a considerable period of time, but the way he is progressing, everybody is pretty happy with him."
Lambert fears a lack of proper rest time may have led to the injury but praised the player's positive approach.
"He played a lot of games with Genk before he joined us, so he never really had that much of a break," added the Scotsman.
"The amount of games he's had here, and playing for the national team, never gave him that breathing space.
"He never mentioned he was fatigued or anything, he just kept on going.
"It's the first time he's been injured since I've been here, but hopefully, as I've said, it's not too bad."