The champions of the English Premiership kept maintained their clean sheet, with a 0-0 draw with FC Koebenhavn, which played host to the City side.
Leicester had won the first leg match at home.
Just as he did when the two sides met two weeks ago, Kasper Schmeichel made a brilliant late save to deny Andreas Cornelius a goal.
Kusk crossed from the right and Cornelius sent a downward header towards the bottom right corner, only for Schmeichel to plunge to his right and claw it out.
The rebound came to Santander, a few yards out, but without composure, he slashed it high and wide.
FC Porto’s 1 – 0 victory in the game against Club Brugge, extended Leicester’s day of celebration, since they need to play another game to be sure of qualification for the last 16.
In Group H, Juventus and Lyon drew 1-1 while Sevilla defeated Dinamo Zagreb 4 – 0.