The Welshman took part in a training session on Tuesday morning after making his comeback from a six-week back injury lay-off as a substitute in the 3-3 draw at Wolves on Sunday.
That appeared to put the 21-year-old in line to start the Champions League second leg at White Hart Lane, but Redknapp has confirmed his star winger is likely to begin the last-16 clash on the touchline after he felt stiffness in his legs following the session.
Redknapp on Tuesday said: "Gareth trained this morning, he still felt a little bit stiff. His back was okay but he felt a little stiff in his legs so we will wait until tomorrow to see how he is. It's touch and go. At the moment it would be doubtful whether he would be fit to start."
Redknapp was boosted by the news Rafael van der Vaart is fit to start against Milan after he missed the game at Molineux with a calf injury.
Younes Kaboul, Vedran Corluka and Ledley King all trained and could also play.
Source: PA
Source: PA