The former Liverpool winger is eagerly anticipating Wednesday's match at the Santiago Bernabeu, and believes Cimbom can spring a surprise
The Spanish wing-back realises the Liga champions head into the quarter-final tie as the favourites, but is nonetheless optimistic about his side's chances to progress.
"Can we knock out Madrid? Why not ... We have enough talent to play against anyone, honestly. People are going to be surprised by us because we're going to attack with everything we have," Riera was quoted as saying by Marca.
"If we get a good result in the first leg, watch out in the return leg, because at home we could seal it.
"Obviously, the Real Madrid players are used to this sort of atmosphere, but we aren't going to give up. They're the favourites, it’s true, but anything is possible."
Galatasaray last made it to the quarter-finals of the Champions League in 2000-01, when they were beaten by Madrid 5-3 on aggregate.