The former Liverpool man believes securing the signature of the highly rated Dutch star is just the beginning at Old Trafford.
The highly-rated PSV Eindhoven and Holland forward was secured on a big-money transfer on Thursday, with United having to move early to secure the player ahead of French giants PSG - per the BBC.
Louis Van Gaal is expected to be busy during the summer transfer window as he looks set to revamp the squad at Old Trafford, and Redknapp believes the signing of Depay will mark the start of a revolving door policy at the club.
“Memphis Depay is just the start of Manchester United’s transfer business this summer,” he said.
“It’s going to be a revolving door there at the end of this season, with an awful lot of comings and goings. [He] is a good start for them, he’s an exciting talent.”
The young forward has had an impressive season for his current Dutch employers, with his consistent performances having helped to guide them to the Eredivisie title.
He was also part of Louis Van Gaal’s Holland squad at last summer's World Cup finals, with the current United manager having given him his international debut in the first place.
That relationship was likely key to him signing on at Old Trafford, with there clearly a level of trust and understanding there. While his relationship with the manager is likely to make his first season in England an easier one, Redknapp says it will be interesting to see how Depay adapts once he’s in the Premier League.
“It will be interesting to see how he adapts,” he added.
“We’ve seen plenty of highly-rated players come from Eredivisie, some have been hits, some have been misses. [However] he’s had a really good season for PSV and can play across the front, particularly starting from the left and cutting in on his favoured right foot.”