The Portuguese winger leads the Premier League's goalscoring charts this season with 17 goals.
Redknapp added: "He is an amazing player - he's got the lot really. He's big, strong, six-foot tall and great in the air."
The Pompey boss also admitted that, despite all of Manchester United's attacking talent, he was looking forward to making the trip to Old Trafford with his team.
"They are a club with great tradition. It's a special place to go and play football. It's a special club," he said.
"I saw the Busby Babes' last game before the Munich disaster and saw probably the finest game of football I've ever seen.
"They've got such great talent they can rip you to pieces."