Morrison bagged a brace as QPR beat Birmingham City 2-0 on Saturday, with Blues boss Lee Clark likening the 21-year-old to Paul Gascoigne.
Redknapp also lauded the youngster's performance at St Andrews, and says that former Red Devils manager Sir Alex Ferguson recommended the player when he was 12 years old.
"What a player he is," the QPR manager told Get West London.
"I've followed his career from when he was a 12-year-old and what Sir Alex told me. For whatever reason he's been let go, but we're glad we've got him.
"He's a real talent and he rode tackles and took his goals well. We wasted opportunities and they were always in the game - but this is a massive win for us."
The victory was their first in six games, but the Rs remain eight points adrift of the automatic play-off spots following Burnley's 2-1 win over Blackburn on Sunday.
However, Redknapp is still hopeful of a return to the Premier League and was thankful that fellow promotion candidates Derby and Nottingham Forest fell to defeats on Saturday.
He said: "They were big results and vital games. There are no easy games in this division."