"I think the Ferdinand deal has gone now," Redknapp told BBC Sport Online.
"It looks like Spurs want to keep him but maybe one or two other Premiership clubs have been alerted now, so he may move - but not to us.
"He would have been a good player for us, for sure."
With only two fit strikers in Mark Burchill and Svetoslav Todorov currently available to Redknapp, he may now make a renewed effort to sign Derby's Deon Burton.
Burton, whose recent loan spell at Fratton Park was cut short by a foot injury, has now asked The Rams for a transfer.
"You need four strikers at the club for the two front positions, so we need to get a couple in," added the Pomey boss.
"People laugh when I say we need to sign more players at this club but we have trained all week with only 12 players."