The footballing world awaits with bated breath - could this really be the end of one of the most dominant dynasties in recent football history?
Spain have to find a way to bounce back from their truly stunning 5-1 defeat to Netherlands - the biggest loss ever suffered by a defending champion at a World Cup.
They are notoriously bad starters at tournaments. Four years ago they went on to become the first team to lift the World Cup having lost their opening game, when they were shocked by Switzerland.
But this is different. Friday's thrashing was so damaging that it is going to take some recovering from. Midfielder Xavi said it was the worst defeat of his long and storied career, while coach Vicente Del Bosque said after the game that the result was "unexplainable".
How they must wish they could switch their fixtures around and face Australia now rather than a red-hot Chile side whose quality has got Del Bosque "worried".
Chile's dangerman is a player the Spaniards know all about. Alexis Sanchez will line-up against a host of his Barcelona team-mates and is in superb form.
He scored one and assisted another as the Chileans raced in a 2-0 lead after 14 minutes against Australia, but it certainly wasn't plain sailing after that and their lack of height at the back, a real weak point for them, was exposed by Tim Cahill.
These two sides met in the Maracana Stadium in 1950 - the last time Brazil hosted the World Cup. Spain won 2-0 in front of a reported crowd of just 16,000 - the final was watched by an incredible 174,000. It's not a ground the current crop of Spanish players have fond memories of, though, having lost 3-0 in the final of the Confederations Cup to Brazil last year.
That defeat exposed weaknesses in a previously unbeatable line-up. The defeat to the Netherlands exposed even more. Will Del Bosque continue show loyalty to a crop of players that have brought so much success, but now look tired and one-dimensional, or try to freshen things up to salvage their dream of becoming the first side since 1962 to retain the World Cup?
The Spain coach said: "There will be changes, but few. We can't blame anyone, we lost the game. We just have to look forward. In life, there are solutions for everything. It's still in our hands.
"It's good to be a little anxious, but always in measured doses. Anxiousness can also allow you to play better. The worst thing would be indifference."
Spain's Barcelona midfielder Andres Iniesta admitted: "We have to win by whatever means necessary.
"I feel that we are prepared to win. We had a tough start and I feel like what happened (Friday) is in the past. We had the same situation in the last World Cup, but this time is different."
Chile have never beaten Spain, but know a draw would represent a positive result after the 3-1 opening game victory over the Australians.
Midfielder Marcelo Diaz, 27, said: "A draw is not bad, but this group of players does not come with the idea to draw a game. We came out here with the idea of winning."
- Chile have never beaten Spain in 10 previous encounters (D2 L8).
- Spain have won their last two meetings with Chile at World Cups. They won 2-0 in 1950 at the Maracana Stadium, where this match is taking place, and then 2-1 in 2010.
- The last time Spain lost back-to-back internationals was in 2006 (3-2 v Northern Ireland and 2-0 v Sweden).
- Their 5-1 defeat to the Netherlands was the first time they had conceded five goals in an international since losing 6-2 to Scotland in June 1963.
- They had only once before conceded five or more goals in a World Cup game (6-1 v Brazil in 1950).
- The Spaniards conceded more goals in 90 minutes against Netherlands than they had in their previous nine internationals combined (four).
- Spain's 5-1 loss to the Netherlands was the heaviest margin of defeat by a reigning World Cup champion in the history of the tournament. The previous heaviest defeats were Brazil losing 3-0 to France in 1998 and West Germany losing 6-3 to France in 1958.
- Chile have lost their two previous World Cup games against the defending champion, both against Brazil (in 1962 and 1998).
- Alexis Sanchez has been involved in seven of the last eight goals that Chile have scored (six assists and one goal).
- Against Australia, Sanchez became the first Chilean to score a goal and provide an assist in a single World Cup game since 1962.
- Chile scored three goals in a World Cup game for the first time since 1962.