Jonathan Woodgate could miss the remainder of the season with a groin injury.
"I don't know if we'll get him back before the end of the season," said Spurs manager Harry Redknapp
Woodgate has played just two league games this term and has gone to the US for a month to work with a specialist to try and cure the injury.
With Woodgate's injury and Ledley King's ongoing knee problem, Spurs are trying to sign defender Younes Kaboul.
"There's a deal there for Kaboul," said Redknapp. "I've been speaking to Portsmouth manager Avram Grant.
"Avram said, 'we need to sell them Harry because ... otherwise we're in trouble'," - a reference to Portsmouth's perilous financial position.
Spartak Moscow's Croatia keeper Stipe Pletikosa is also arriving to see the Spurs' medical staff before the transfer window closes on Monday.
The 31-year-old, Croatia's first-choice, damaged cruciate ligaments in training in August and needed surgery.