Celtic manager Neil Lennon has paid tribute to the "absolute courage and positivity" of Stiliyan Petrov after his former Parkhead team-mate officially confirmed his retirement from football.

Aston Villa's Bulgarian midfielder Stiliyan Petrov announced Thursday that he is quitting professional football as he continues his fight against leukemia. Petrov is now in remission after being diagnosed with the illness in March last year.

"Obviously it's very sad that Stiliyan has announced his retirement from football,” Lennon has told Celtic’s official website.

"He was a fine footballer and enjoyed a magnificent career at Celtic and Aston Villa, as well as representing and captaining Bulgaria on many occasions.”

"I'm sure that Stiliyan's characteristic determination, along with the fact he's surrounded by a loving family, will ensure he's a success in this next stage of his life.”

Lennon has remained close friends with Petrov since the Bulgarian departed for Villa in 2006.

A number of stars of the footballing world, including Wayne Rooney, Vincent Kompany and Stan Collymore, have reacted to Petrov’s retirement on Twitter, wishing him good luck and praising his courage.

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