The experienced Argentine missed last week's 2-0 first-leg loss through suspension, as Benfica succumbed to efforts from Nicolo Barella and Romelu Lukaku in the second half.
Otamendi will take his rightful place in the backline here - forcing Morato out of the team - as the much-coveted Antonio Silva also lines up in front of Odisseas Vlachodimos.
Right-back Alexander Bah is expected to miss up to a month with a knee injury, so Gilberto will hold the fort on that side as Alejandro Grimaldo charges down the left flank.
Midfielder Florentino was unavailable for the weekend's Primeira Liga defeat to Chaves due to a ban, but the 23-year-old is eligible to return here and could displace Chiquinho in a 4-2-3-1 setup.
Fredrik Aursnes is in line to partner the returning Florentino, while Julian Draxler and Mihailo Ristic are both nursing muscular problems but would have been unlikely to demote ex-Inter man Joao Mario, who is thriving with 23 goals to his name this season, but he gave away the penalty which led to Inter's second last week.
David Neres and Rafa Silva will expect to complete the attacking quartet alongside marksman Goncalo Ramos, who has found the net 25 times this term but is without a goal in his last three games.
Benfica possible starting lineup: Vlachodimos; Gilberto, A. Silva, Otamendi, Grimaldo; Florentino, Aursnes; Neres, R. Silva, Mario; Ramos