The 26-year-old, who made his senior debut in 2005 after coming through the youth ranks at City, moved to Serie A side Fiorentina on loan in the summer.
During an interview with The Guardian, Richards recalls the moment when he was pulled off at half time while 2-0 down against Watford in an FA Cup match, which City went on to win 4-2 back in January last season.
"I've not always played well for City, but I'd never been the scapegoat, coming off at half time when in my head I thought I was having a decent game," Richards told the newspaper. "It was weird, unnatural, it had never happened to me before and it felt like no matter what I did it wasn't good enough any more. That was a turning point.
"The manager did try to explain it to me. He said he didn't want to rush my fitness, but I wasn't playing in the Premier League, I wasn't playing in the Champions League, so at least, in the FA Cup against Watford at home, give me 90 minutes. After that, my belief was shattered."
Richards made his debut for Fiorentina in last night's 3-0 win over Guingamp in the Europa League.