Barca are not known for being shy in front of goal but they have been an unstoppable force at Vallecas in recent years, following up a thumping 7-0 win with last season's 5-0 victory in Madrid.
The history books are a little kinder to Rayo, however, with the capital club registering two wins and two draws against the Catalans on home turf in the early 2000s.
Skip to the present and Paco Jemez's men are struggling again. Despite beating Elche 3-0 on the opening day, they have lost three games in a row.
Two of those matches - against Atletico Madrid and Malaga - saw them ship five goals without reply.
With all the relevant facts and figures in mind, Rayo midfielder Trashorras felt unable to either trade on past glories or to write his side off, instead insisting Barca were there to be beaten.
He told his club's official website: "I'm not looking at the results of past years. It's a game where we have a lot to gain and little to lose.
"We're going to compete and three points would earn us a lot of prestige.
"But we are facing one of the best teams in the world.
"The main thing we need to consider if we're going to compete, if we're going to get something positive out of the game or even to win it, is that we need make the most of the chances we do get.
"We have to believe that chances are there to be taken and that is the only way. We need to go out there thinking that anything could happen.
"No team has won every game through a whole season and if we do things well and put on our best performance then we can compete."
The fact that Barca coach Gerardo Martino considered Wednesday's 4-0 Champions League victory over Ajax to be less than "brilliant" should further depress Rayo's players but Trashorras remains optimistic.
"What we have to do is exhaust all possibilities against a team who we know are capable of dominating all aspects of a game," he added. "Everyone has to play at their highest level.
"Playing at home is a major factor for us to consider. We have to keep possession as much as we can and survive as best we can when we don't have the ball."
Mexican winger Nery Castillo is back in training at the Ciudad Deportiva, alongside on-loan Tottenham midfielder Iago Falque. Alhassane 'Lass' Bangoura and Jose Carlos are unlikely to feature, though.
Barca have concerns in defence with Carles Puyol and Jordi Alba both struggling while Gerard Pique (groin) needs a late fitness test before travelling to Madrid.