Werder Bremen midfielder Philipp Bargfrede has been ruled out for three months undergoing knee surgery, the Bundesliga club have confirmed.
The 24-year-old injured himself on Sunday when he twisted his knee in a pre-season training session and he underwent investigation by a knee specialist on Tuesday, who determined he needed surgery.
Bargfrede had a procedure today in Augsburg to reattach his lateral meniscus and will now have to begin a three-month rehabilitation programme.
Bremen coach Robin Dutt said: "It has unfortunately confirmed what we had feared after the initial examination.
"The meniscus had to be sewn on. I feel very sorry for Philip. He has made an excellent impression in the first days of training."
Bargfrede only made 13 appearances for Bremen last season following Achilles problems and an earlier knee injury.
After twisting his knee during the training session, he said: "It is totally aggravating for me. I was out in the winter after only a few days of training and now it happens to me again."
The game on September 8 will celebrate the career of fellow former Hoops player Petrov, who announced his retirement in May as he continues his battle with leukaemia.
Ex-Celtic, Manchester United and Barcelona striker Larsson is aiming to make a fleeting return to the east end of Glasgow after giving his backing to the match.
He told the club's website: "If I can make it, I will come.
"I've said that all along but it depends what's going to happen with my working situation. But if I get an hour or two I will fly over and come and play the game!
"I would definitely like to take part in the game. I've always said that it's a great place. That's where I made my name and that's where I became the player I was - I absolutely love the place."
Funds raised will go to Celtic Charity and will support Petrov's nominated charities, as well as other projects and causes within the local community and beyond.
Larsson added: "Obviously I was very saddened when I heard the news of Stan's illness.
"He's a player and a man that I know very well and we shared a lot of things together.
"It was very saddening when I heard it, but you don't think only of him, you think of his family as well.
"He's a strong guy and you just hope that everything goes well because he's a fantastic guy and I'm looking forward to seeing him."
Meanwhile, BBC Scotland and BBC Northern Ireland have secured live rights to Celtic's Champions League qualifier against Cliftonville at Solitude on July 17.
