It was Benteke's first appearance since he signed his new contract.
Lambert told AVTV: "It was just another fitness thing tonight. Luton did really fine against us.
"The pleasing thing was Christian being back. Some of his touches were brilliant.
"He had 45 minutes. He's only done a bit of training. He's still got to work on match fitness but that 45 minutes will do him the world of good."