The Welshman took part in a training session on Tuesday morning after making his comeback from a six-week back injury layoff as a substitute in the 3-3 draw at Wolves on Sunday. That appeared to put the 21-year-old in line to start Wednesday's second leg at White Hart Lane.
However, Redknapp confirmed on Tuesday that his star winger is likely to begin the last-16 clash at White Hart Lane on the touchline after he felt stiffness in his legs following the session. He 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 Wednesday to see how he is."
He added: "It's touch and go. At the moment it would be doubtful whether he would be fit to start."
Bale's loss is a big blow to Spurs but Redknapp will take comfort from the knowledge that his side beat the Rossoneri 1-0 without him three weeks ago in the first leg of the last-16 tie at the San Siro.
Redknapp was boosted by the news that Rafael van der Vaart is fit to start on Wednesday after he missed the game at Molineux with a calf injury.
Younes Kaboul, Vedran Corluka and Ledley King all trained on Tuesday morning and could also play.
Source: PA
Source: PA