The 27-year-old was linked with a move to Carlo Ancelotti's side, as well as Premier League champions Manchester United, while Coentrao's future at the Bernabeu hung in the balance on transfer deadline day - but the Portuguese did not complete his rumoured move to Old Trafford.
Primeira Liga giants Benfica were therefore able to push through a loan deal for former Inter Milan, Lazio and Udinese defender Siqueira and confirmed the transfer on their official website.
A statement read: "Benfica have secured Guilherme Siqueira on a one-year loan deal for the 2013-14 season.
"The Brazilian left-back, 27, arrives from Granada, where has played since 2011.
"Before playing for Granada, Siqueira played for Avai, Ipatinga, Inter Milan, Lazio, Udinese and Ancona."
Siqueira originally joined Granada in a co-ownership arrangement with Udinese three years ago, helping the Andalusians win promotion to the Primera Division before signing a four-year permanent contract in June 2011.