The Argentina international completed his transfer from Sevilla on Wednesday and trained with the squad on Friday.
The central defender will wear number 21.
Kyle Naughton is also available again after serving a one-match Premier League suspension for his sending off at West Ham. He returned to action against AEL Limassol on Thursday night.
Mauricio Pochettino will make a late decision on the fitness of Roberto Soldado, who missed our 3-0 win against AEL due to stiffness in his back and neck. Kyle Walker (pelvis) remains sidelined.
Nabil Bentaleb, Etienne Capoue, Christian Eriksen, Erik Lamela and Jan Vertonghen - all rested for AEL on Thursday - are all back in contention to face Liverpool.