Rayo know even an unlikely win would not lift them out of the bottom three in the Primera Division table because of their poor goal difference, but that has not deterred the Madrid-based side from going in to the game with a positive attitude.
A 4-1 home win over Malaga in their last league fixture lifted the spirits of the Rayo players.
Baena told his club's official website: "In recent games I was seeing a improvement in the team but we had to improve to win a game.
"It was essential for us to win against Malaga and it gives us great moral to face what is coming.
"We are excited (to face Barcelona) and know it will be difficult but we will do everything possible to get something positive out of the game.
"Barcelona is not the ideal place to look to get a victory, but we will do everything possible."
Vallecano will have Romanian defender Razvan Rat available after he signed for the remainder of the season as a free agent following his release by English Premier League side West Ham.
Barcelona coach Gerardo Martino is boosted by the return to training of Brazilian forward Neymar.
A tendon injury to his right ankle - suffered against Getafe in a Copa del Rey match - kept Neymar out of action for a month, forcing the Brazilian to miss eight games.
But after receiving medical clearance to resume training Neymar joined in with his team-mates on Friday and is back in Martino's squad for the game with Rayo Vallecano.
Martino told a press conference: "Neymar has trained very well. But this does not change anything. All (players are) competing for a chance."
The visitors will not only have to contend with Neymar but also the mercurial talents of Argentinian playmaker Lionel Messi who is closing in on a club goalscoring record.
Messi has scored 11 league goals this season out of his total of 22, putting him on 226 league goals in Spanish football.
That places him one behind former Real Madrid star Alfredo Di Stefano (227) and two fewer than La Liga's leading all-time scorer Raul who netted 228.
Martino added: "Messi had the flu, he had a stuffy nose. But the doctors told me it was not serious."
Martino has decided to leave out Xavi due to injury.
He said: "Xavi is fine. He has been left out of the squad and has therefore trained in the gym."