Redknapp told The News of the Nigerian: "I thought he was excellent. He showed he's got good feet, is quick, strong, can play through the middle and can play wide. He'll be a threat to teams for sure. When I went to watch him at Rennes he played up front with Jimmy Briand, who was a good player.
"I liked the pair of them, I tried to get the both of them, to be honest - they were terrific together. It's funny when you bring new players in.
"I looked at him in training and suddenly I've thought 'I'm not sure'.
"He looked quite a laid-back boy and I've started to get worried about him and thinking whether I have made a ricket there. But when I went to see him at Rennes last year he always did great, so I'm thinking 'Wait until the games come, wait until the games come'.
"Sure enough, he showed what he can do. You could see John's got quick feet, plenty of skill and he can rip you to pieces.
"Andy Griffin's not an easy guy to beat, he's low to the ground, he's aggressive and dogged. But John troubled him and I know he will do well for us."