The 33-year-old was diagnosed with acute leukaemia last year, but after high intensity treatment, the disease is now in remission.
But despite beating his illness he has chosen to call time on his playing career, and Lambert would like to see him back at Villa Park in a coaching capacity.
|PETROV RETIRES FROM FOOTBALL
|100/1||Aston Villa are 100/1 with William Hill to be relegated
"I am not sure whether that would be on a full-time or a part-time basis. The door is always open to him here and that has nothing to do with sentimental reasons."
Petrov will lead the players on a lap of honour in their final home game of the season against Chelsea on Sunday.
Lambert has known the Bulgaria international since he was 19, when they played at Celtic together, so he is thankful that he has made a recovery.
He added: "The most important thing is that he has survived that horrible disease. You cannot imagine what people with that illness go through. I am delighted first and foremost that he is alive.
"The fact he is going out there onto the pitch on Saturday will be incredible. It will be a great occasion. The support for him, including the 19th-minute applause, has been magnificent not just from our supporters but other fans at other clubs and other coaching staffs.
"Everyone has got behind it and it will be a very emotional day for all of us. Missing him as a player has been a huge blow. Trying to replace a fantastic player like him is so hard, but he is a wonderful man. He has a heart of gold. I have known him since he was 19.
"I played with him for nine years and he is a fantastic character. Whatever he chooses to do in the future, we wish him all the best."