The on-loan Manchester City striker picked up a hamstring strain in Spurs' victory over Arsenal on Sunday, October 2.
The 27-year-old has been rated as 50/50 for the match at St James's Park, but Redknapp doesn't want to make a potential injury any worse.
"It's a dangerous one," said Redknapp. "If he tears it badly, he has got a grade one tear if he makes a real mess of it and he could be out for six or seven weeks.
"If he is a doubt, I wouldn't want to risk him. I wouldn't want to lose him long term."
Tottenham are currently sixth in the Premier League table, while Newcastle occupy fourth place.