Despite declaring that he wanted to leave for Chelsea earlier this summer, the Croatian was given a hero's welcome as he came on as an early substitute just before Tottenham went behind during a poor first-half display.
The introduction of Gareth Bale and five other substitutes at half-time buoyed the home side, who scored two goals in two minutes from Peter Crouch and Jermain Defoe to seal victory.
Spurs struggled to get into their stride in the first half and their only real chance of the opening period came when Niko Kranjcar shot wide while in space 10 yards out.
Steven Pienaar suffered a stomach injury in the 24th minute and Redknapp opted to replace him with Modric.
Modric received a fantastic reception as he entered the pitch, the home support having seemingly forgotten about the Croatian's public pleas to leave for Spurs' rivals.
The euphoria that greeted Modric's arrival disappeared within seconds as Mikel San Jose lost his marker to tap home a free-kick to put the Spaniards ahead.
Spurs were scrappy in possession, with Michael Dawson and Tom Huddlestone giving away the ball on several occasions.
Redknapp reshuffled his team at half-time, bringing on Brad Friedel, Bale, Crouch, Defoe, Kyle Walker and Younes Kaboul.
The move worked wonders, with the newcomers injecting life and pace into what had previously been a dull display.
Tottenham were level five minutes into the half when Bale burst down the left and found Crouch at the back post where he acrobatically poked home from six yards.
Two minutes later Tottenham were ahead. This time it was Defoe's turn to tap in from close-range after a clinical cross from Aaron Lennon.
Reported Spurs target Fernando Llorente provided Redknapp with a glimpse of his skill when he beat his marker from six yards only to see his shot rebound off the woodwork for the Basque side.
Carlos Gurpegi then upended Lennon in the box to give Spurs a chance to move further ahead in the 70th minute, but Gorka Iraizoz tipped wide Kranjcar's sloppy penalty.
Bale had an appeal for a penalty turned down with five minutes left and Crouch stung Iraizoz's palms with a bullet header from six yards at the death.