The 37-year-old played for Aston Villa in a friendly recently.
The legendary midfielder featured in Aston Villa's 8-0 friendly win over Graz for what was his first Villa appearance in over four years.
The former Celtic man has won his battle with acute leukaemia since then, and Amavi, who joined the club last summer, says it was lovely to see the 37-year-old back in action.
"Talking of the GAK Graz match, it was tremendous to see Stiliyan Petrov out there," he told Aston Villa's official website. "I didn’t know Stan before I arrived at Villa but obviously I had read his story.
"To see him on a pitch playing professional football again was, in my ways, unbelievable. You sometimes questioned what you were seeing considering he was diagnosed with leukemia four years ago and had to fight to save his life.
"This story is one that goes above football. It’s a story of how important courage, persistence and determination are in life."
Petrov is training with Aston Villa but he is not contracted to the West Midands club and it remains to be seen if he will have any role to play in the Championship this season.
The Bulgaria international, who has 105 caps for his country, enjoyed a seven-year spell at Aston Villa until 2013, when health reasons forced him into a hiatus.
He joined Villa after earning legendary status at Celtic too, having also spent seven years at Parkhead. Martin O'Neill, who managed him at Celtic, brought him to Villa Park in 2006.