Saunders played under Smith at Brentford, while he is Terry's business partner in their luxury swimwear brand Thomas Royall.
The Wycombe midfielder told the Mirror: "John's been working on his badges over the last couple of years but he's been a leader his whole career. The players already respect him.
"Dean did a good job at Brentford and plays a great style of attacking football. He's very hands-on in training but will sometimes take a back seat and let the rest of his coaches take charge.
"He's well mannered, not a screamer or shouter, but if he wasn't happy you would certainly know about it.
"He's a good guy, very honest. His door is always open and he has good conversation with his players.
"When I wasn't in the team, he never made me feel excluded from the lads. It's a good trait to have, especially with a big squad like Villa where it will be difficult to keep everyone happy."