Muamba has been touted as an outside chance of making England's World Cup squad.
"When I left Arsenal, I went to see Arsene Wenger and he was not particularly sure about my future. I just decided that if he wasn't sure then I was just going to make a future for myself," said Muamba.
"I have never looked back. It's probably the best decision I've made.
"People at Arsenal said I wasn't good enough, that's their opinion. I'm doing more now than they ever expected. So it's their loss."