Celtic flop Hayato Inamura insisted he was never given a chance at Parkhead, but admitted he was stunned at the higher level of football in Scotland.
The 23-year-old Japanese defender was sent back to his homeland last week after just six months at Celtic to complete a loan deal with FC Tokyo.
He made just one appearance for the Scottish champions since joining on a four-year deal from Albirex Niigata last summer.
And he has admitted his time in Glasgow was a nightmare.
Inamura said: “It was difficult in many ways. It was a tough time for me. There are things I can say and things I can’t say. But there really was a difference in football ability.
“I was confident I could reach that level if I could play in the games, but I wasn’t given the chance. And I had mental ups and downs.
“Daizen Maeda told me I could definitely launch my career again if I returned home to Japan and that encouraged me.
“After thinking about what I needed for my career, I decided to move to FC Tokyo.
“I want to test myself and work hard to reach a higher level.
“My first priority will be to break into the team because there are good players here.”