Lambert told BBC Sport: "I knew [Keane] had a lot of football knowledge that was unfairly tarnished. His knowledge meant he was too good to be a TV pundit. To get him back in the game was great. I love working with him, we have a laugh.
"When I was thinking about people to bring in, I know it probably raised a few eyebrows, 'How's that going to work?' Nobody sees the logic in it. I just knew in my gut it would work.
"He's been great around the place, with the staff and the lads. He's somebody I know I can rely on. I never had any doubts. He was the first port of call when I knew I had to get somebody in."
Aston Villa take on Arsenal this afternoon in the Premier League.