Each week they face small obstacles which they usually jump with ease, though once in a while they catch themselves and briefly lose their rhythm. Sooner, rather than later, they will look across and see each other head-to-head. Each time only one can triumph.
One of the two will win Spain's Primera Liga — though that could have been said in September, thanks to the crushing predictability of the league in marked contrast to the glorious football it sometimes produces.
Both teams won at the weekend and are well clear of the field, but with Barca, the champions, still enjoying a five-point gap over their greatest rivals, even Real concede that the league is the Catalans' to lose.
With just nine games remaining, time is running out for Real, though Barca's visit to the Bernabeu next month could trip up Pep Guardiola's side. Real have won every home game this season, but they also lost 5-0 when they last faced Barca.
Real are all the stronger now for Jose Mourinho conquering the club's internal demons. He is doing things his way and has come good at the right time.
The pair will also meet in the final of the Copa del Rey, the Spanish Cup, in Valencia, which is the first of a potential four clasicos in just over two weeks.
Spain awaits; the football world does, too. More than 70,000 Barca fans applied for less than a third that amount of tickets at the Estadio Mestalla.
Spain's big two are also first and second favourites to lift the Champions League, Real finally shattering the curse that restricted them to the last 16 for six consecutive seasons with last week's victory over Lyon. They will face Tottenham Hotspur of England in the last eight.
Barca's victory over Arsenal set them up with a quarter-final against old foes Shakhtar Donetsk, after that their potential quarter-final opponents are - Real Madrid.
Both clubs are well positioned exactly when it matters, but both have issues which could knock them out of their stride. Real's free-scoring talisman Cristiano Ronaldo will be out for two or three weeks with a thigh injury and is a doubt for the quarter-final first leg against Tottenham on April 5.
Barca were rocked by the news that Eric Abidal, their best performing defender so far this year, has liver cancer.
He was treated on Thursday in Barcelona amid a wave of public support which saw sales of shirts with his name on rise by 3,000 per cent in the club shop.
His teammates (and players from opponents Getafe) wore T-shirts with a message of support for the France international, who wears the No 22 shirt, as they walked out on to the pitch. There was an ovation for Abidal in the 22nd minute.
Both clubs will look to their strengths. Karim Benzema has become Europe's most in-form striker.
Derided and neglected by his own coach at the start of the season, Benzema continues to prove Mourinho wrong week after week and scored again in Saturday's fortuitous 2-1 win at neighbours Atletico.
Lucky because Real tired badly towards the end after their European exploits, yet Benzema's neat chip over David De Gea was his eighth strike in five matches.
"Benzema is on a run and we have to make the most of it," Iker Casillas, his captain, said. "He has made a radical change and we are very happy."
"The next two months will be intense," Real's Xabi Alonso said. "We will try to live up to the challenge and thrill the fans."
Spain and, indeed, the rest of the world certainly hope so. Game on.