Tottenham are sweating on the fitness of William Gallas after seeing the centre-half pick up a knock.
The Frenchman has damaged his hamstring and could be facing up to a month on the sidelines.
The 33-year-old pulled up with the problem in training on Tuesday, handing Spurs an unwelcome injury blow.
Gallas was immediately sent for a scan in an effort to determine the full extent of the problem, but the results of those tests are yet to be revealed.
Redknapp admits he is uncertain as to how long the former Arsenal and Chelsea man will be out of action for.
He said in The Sun: "It's not good. William just pulled up and now we have to wait and see whether there's a tear.
"William's been in great form for us. If he's out for a long time it's a big blow for sure."
Spurs were also given a scare by Gareth Bale on Tuesday, as he was forced to finish training early after taking a knock to his thigh.
The club are confident, however, that the Wales international, who recently missed six weeks with a niggling back problem, will be ready to face capital rivals West Ham on Saturday.
