Redknapp wrote in The Sun: "In fact it will be much tougher taking over now than it was for Alex Ferguson when he walked into Old Trafford back in 1986.
"Back then Manchester United were struggling in the league, so the only way was up really.
"There was not the same expectation placed on the team and the management.
"And because Alex Ferguson was allowed the time to build a team, he was able to do it without any undue pressure.
"No disrespect to United this season — because they have been very consistent and played some good football at times.
"But let’s face it they walked the league.
"Next season will be totally different.
"There will be even more teams capable of mounting a serious challenge."