The Barnsley midfielder was shown the door at Stamford Bridge a year ago after the club took a dim view of a prank where he set off a smoke grenade.
Mellis, 22, insisted: "I wouldn't say it's something I've really had to recover from - I've just had to move on. I don't think I've paid for it.
"People will look at what happened and say whatever, but I don't think I was ever going to play for Chelsea's first team week in and week out. There have been no other incidents since then, so I'm just concentrating on my football now."