With the scores level at 1-1 after the first leg at the Bernabeu, Real Madrid's approach to last night's Copa del Rey match at the Nou Camp is almost certain to be the the way they tackle Manchester United at Old Trafford in the Champions League next Tuesday.
Therefore, it was no surprise that Sir Alex Ferguson was in the stands. And the Manchester United manager will have plenty to think about after Jose Mourinho's side produced a near perfect performance against a side many consider the best in the world.
Madrid allowed Barca to dominate possession but denied them the space to work their magic, just as AC Milan had done when surprising Andres Iniesta and co in their 2-0 Champions League last 16 first leg victory last week.
Cristiano Ronaldo outshone World Player of the Year Lionel Messi, scoring in a record sixth consecutive 'Clasico' away from home, the first goal coming from the penalty spot and the second after a trademark fast counter-attack.
The match ended 3-1 with Real Madrid progressing to the Copa del Rey final 4-2 on aggregate, and it was a result that will ensure Los Blancos fully believe they can progress on the European front when they meet Manchester United.
"We want to continue in the same vein," Ronaldo told Spanish television last night. "This game gives us enormous confidence for the trip to Manchester."
While Real Madrid may have discovered the formula for progressing after a 1-1 first leg home draw, Ferguson's attendance ensures the Manchester United manager has a week to find an antidote.
It is almost inconceivable that Manchester United will be as poor as Barcelona were last night, and the Premier League leaders are certain to ask more questions than the La Liga leaders who seemed incapable of any other line of attack than through the centre of the pitch.
That Real Madrid will tackle United in the same way as they did Barcelona seems likely, with goalkeeper Iker Casillas, who is currently out injured, suggesting as much.
The Spain goalkeeper said: "We have to transfer this to the match against Manchester United. It is also 1-1 and we have to score and keep a clean sheet. That's the aim that we're going with.
"Manchester United know how to play football, it is a difficult place to go to and we have to take what we have done (against Barca) to Old Trafford."
Last night's victory for Real Madrid will have come as a huge relief. Trailing Barcelona by 16 points in the league, their chances of retaining their crown are next to nil. The United tie has been described as 50-50 by Mourinho meaning defeat last night could well have distinguished all their hopes of silverware this season.
"Hopefully this is a turning point to have won this tie and to make it better it was against Barcelona," said Casillas.
"We played a very good tie all round and this will motivate us to make a good showing of ourselves in other matches. Winning the Champions League is a better possibility than the league, but Real Madrid will fight to the end."
Before facing Manchester United on Tuesday, Real Madrid play Barcelona again, this time in the league. Although the result will have little impact on the destination of the title, Casillas guarantees Real will be fully focused on the match rather than looking ahead to United.
"I know several players from Barcelona and I know they are competitive. We have to be aware that in the league, when we do not win, the fans suffer and it is our duty to fight in every match and the next one is against Barcelona," he said.
"What we want to do is win and keep cutting their lead.
"It is a considerable gap, but with the added bonus of our home fans we want to round off the week well."
Ferguson is sure to tune in again on Saturday afternoon looking for clues, although last night will have provided the basis for how he plans to tackle Tuesday's visitors.