The 20-year-old said: “Celtic is a huge club always fighting for the title, but I think the Championship is more competitive, the football down here is more competitive, every team wants to get to the Premier League.
“You only have to look at the Swansea versus Chelsea game to see how close the games are.”
Janko started only eight games for the Parkhead men in a debut campaign disrupted by injury.
Rodgers brought him in for pre-season and the start of the term, but his dodgy display in Israel convinced the Irishman he needed to strengthen the right-hand side of the defence.
It was Davie Moyes who took the player to Old Trafford on a free transfer from Zurich in the summer of 2013.
Janko didn’t make an appearance in the league and played one game for the Scotsman’s replacement Louis van Gaal – the disastrous 4-0 League Cup loss to MK Dons in August 2014.