It's well known the Real Madrid coach covets the United job.
Redknapp wrote in The Sun: "I'm a huge fan of Jose, it should be a terrific occasion and hopefully, I will be able to get a ticket to see the game.
"It is hardly the greatest secret that Jose is planning - one day - to manage again in the Premier League and it wouldn't surprise me if he ends up in Manchester.
"But I can picture him being at United rather than City.
"When Alex Ferguson eventually calls time on his amazing career, there will not be many serious contenders to take over.
"But Jose, I have no doubt, would be big enough to take on the ultimate challenge and succeed the greatest manager this country has ever seen.
"He would be amazing at Old Trafford. His style would be very different to Fergie's but I'm sure he would get the same amount of success.
"Attempting to manage this great club has broken many managers. Look at when Sir Matt Busby left Old Trafford. The likes of Frank O'Farrell and Wilf McGuinness really struggled as it was virtually an impossible job.
"Taking over from Fergie, whenever it happens, will also be almost impossible.
"But Jose could once again be the special one. If anyone could do it, he could - and United fans would love him."