The striker played under Pochettino from January 2013 – May 2014, before they both left the club.
Speaking to the official Southampton FC website, Lambert said: “I had three excellent managers. The three best managers I had in my career were the ones at Southampton, but the best one was Mauricio Pochettino.
“He was just brilliant, everything about him. On the pitch, technically, he had a different way to look at it, and learning from him was one of the best things I've ever done in football.
“Off the pitch, he really cared about you as well – every single person in the club, from the players to the staff. He really made everyone feel special."