The Swiss international had a serious ankle problem discovered in his Forest medical.
The talented attacker was a hotly tipped signing from Young Boys last summer for Lille and he was expected to shine as a replacement for Salomon Kalou.
He is full of talent but has struggled in France since making the move from his homeland. He has picked up regular injury problems since arriving in Ligue 1, which have resulted in him score just the six goals in 27 games for the club.
Frey has now been speaking about the failed Forest move - suggesting an ankle injury picked up on his medical ended the deal. He also confirmed that he had also held talks with Blackburn Rovers in a conversation with Swiss paper Blick. He even suggested that the Forest medical saved his career:
"Yes. And discussions with Blackburn.
"There, too, I've looked at the training ground.
"In Nottingham I have made the medical tests. And since it has been found that some is not good on my ankle.
"Without this check, I would have continued to play. Under pain. That could mean the end of my career!"
Forest were lucky not to sign him. He has not played yet this season and in fact has not played a game since the middle of January - who admits he is open to a return to Switzerland in the winter.
Forest however are probably likely to stay clear of the player after Dougie Freedman's fears over his injury worries proved correct.