Drogba is off contract in June and yet to settle on new terms with the Blues.
Redknapp said: "He is a free but I was just reading in the paper about him going to China.
"It seems the money in China at the moment is incredible. Players can go there and make a fortune.
"He would be a great player for Chelsea to keep or for somebody else to take. Anyone would be interested but you would have to be able to afford his wages. That is going to be the key. If he is on a free you are going to have to pay him a fortune.
"But he is a powerhouse when he is on his game. He is strong and almost unplayable when he is really at it.
"It was an amazing goal he scored against us. He smashed it from an angle.
"His strength in holding (Spurs defender William) Gallas off and then hitting the ball from where he did, there aren't too many players who could have done that."