Spurs take on the Serie A giants at the San Siro on Tuesday in the first leg of their last 16 tie and Redknapp can give no guarantees with regards to the fitness of three of the club's top performers this term.
"They are all struggling at the moment," he said. "It's difficult to say whether they'll be fit for Tuesday.
"Luka has started jogging but isn't available tomorrow. Rafa has a calf strain and Gareth is coming back slowly.
"We have one or two injuries but hopefully it won't be too long."The Spurs boss also urged his players to concentrate on getting a positive result against Sunderland on Saturday before the focus switches to the San Siro.
Redknapp added: "Tomorrow [Saturday] is a key game for us. It's the one you worry about.
"We are bang in the frame with the top four and are looking to do our best to keep up there so the league games are all important to us.
"Focusing on Sunderland shouldn't be difficult because the players know the importance of it.
"We have picked up six good points recently and the results last week have put us right into the group again.
"There is nothing between the teams pushing for that fourth spot. We have to focus on that now. That's the key thing."
The north London side have already been lighting up the Champions League with a number of stand-out performances in the group stages and Redknapp hopes his side can become regular additions to Europe's elite club competition.
"If we got back into the Champions League again it would be great for us," he continued.
"We have had a great run, we have loved every minute of it and we want some more."
Redknapp also vented his annoyance in the wake of the midweek international fixtures with Spurs midfielder Wilson Palacios having travelled to Honduras for an international friendly despite having been struggling with a knee injury in recent times.
"International week is a nightmare," Redknapp said.
"Wilson played last week when we weren't sure whether he'd be fit and now he has had to go and play in a friendly game all the way to Honduras.
"I'm not sure of the flight time but it's horrendous."
The former Portsmouth boss also responded to recent reports linking Roman Pavlyuchenko with a move away from White Hart Lane, insisting the striker must grasp the opportunity to impress when selected in the future.
"Pav has been talking in the newspapers but when he plays he has to go out and grab the opportunity," he concluded.