The team with the canary-yellow strip spent a year in the second division in 2012-13 but have bounced back in impressive style under coach Marcelino and have won praise for their entertaining, attack-minded play.
Ahead of Sunday's game at Real's intimidating Bernabeu arena, Villarreal are sixth and well placed to secure a berth in continental competition again for next season after finishing in the same position last term.
Before they travel to Madrid, Marcelino's side take a 2-1 lead to Salzburg for the second leg of their Europa League last 32 tie later on Thursday in what will be the opening act in a potentially crucial week for their season.
Through to the King's Cup last four for the first time, they trail Barca 3-1 ahead of the second leg in Villarreal on Wednesday.
"We always play with the idea of going for goal," Marcelino told Wednesday's news conference previewing the Salzburg game.
"We know that when we don't have the ball we have to focus on defending well but when we get it back we are a dangerous team that creates chances," added the 49-year-old, who has had stints in charge at clubs including Sevilla and Real Zaragoza.
Real, who won 2-0 at Villarreal in La Liga at the end of September, are waiting on the fitness of Wales winger Gareth Bale, who has not trained with his team mates this week due to an ankle problem.
Carlo Ancelotti's side appear to have put their recent stumble behind them and have won their last three matches, including a 2-0 Champions League win at Schalke 04, without conceding a goal.
They are four points clear of second-placed Barcelona, who play at Granada on Saturday and cannot afford another slip-up after last weekend's surprise 1-0 reverse at home to Malaga.
Champions Atletico Madrid, three points behind Barca in third, need to pick themselves up after Wednesday's 1-0 Champions League defeat at Bayer Leverkusen when they play at fifth-placed Sevilla on Sunday.
(Editing by Amlan Chakraborty)
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