Rayo Vallecano striker Javi Guerra is taking inspiration from Celta Vigo's heroics against Barcelona for Saturday's trip to Camp Nou.
Celta stunningly ended the defending champions' 100 per cent start to the Liga season with a thrilling 4-1 win at the end of September.
Barca also lost 2-1 at Sevilla ahead of the international break, offering Guerra " who has three goals from five appearances since joining Rayo in August " enough encouragement that an upset may be on the cards.
"In football anything can happen, nobody is invincible," Guerra said.
"Celta has a great team, they play very good football and had an impressive day against a Barcelona that was not on form and did damage.
"When we have the ball we must play forwards and if we there is pressure we can catch them on the break.
"It is clear that Barcelona play with a lot of risk and will leave behind many spaces and can hurt you.
"Let's go without fear and try to take advantage of those spaces to play fast, go forward and have chances."
Barcelona will again be without their talisman Lionel Messi and midfield maestro Andres Iniesta due to respective knee and hamstring injuries.
"I'd rather [they were fit]," Guerra added. "It's nice to face the best and if you get a good result it is better.
"Barcelona are the best team in the world. They have many good things and many virtues.
"They have lost a goal without Messi without Iniesta the final pass, but they are quality players who at any time can change a game.
"We will have to make a match compact, be close together, defend well and keep the ball. It is a match where there in no need to motivate anyone."
History is certainly against Guerra and his team-mates, with Barcelona winning the previous nine meetings between the sides " racking up 40 goals and conceding a mere two in the process.
Messi dazzled with a second-half hat-trick and Luis Suarez netted a brace as Luis Enrique's men won last season's corresponding fixture 6-1 in March.
Such walkovers have not been a feature for Barca this time around and Suarez appreciates the magnitude of the challenge facing them as three points separate La Liga's top five after seven matches.
"We all know how tough our rivals are," Suarez told La Liga's official website. "Both Real Madrid and Atletico, as well as Valencia or Sevilla, among others, have already shown that.
"We have to keep believing in ourselves, understanding that teams make mistakes."