The veteran striker has been outstanding for the Rs in the past two weeks.
"Bobby was out of contract, but that Wembley goal did his confidence a power of good," Redknapp said.
"He feels the fans love him now, and that's also good for his confidence. I made him captain and he gave me a captain's performance, and he enjoyed the challenge in that.
"He's always been a good player. When he was at Fulham he was a fantastic player in my opinion."
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