The versatile forward's movement and goal threat represents a huge challenge to Australia's paper-thin backline in their Group B clashAustralia's slim hopes.
With all the talk surrounding Vidal's recovery from knee surgery, Sanchez has somehow slipped under the radar.
But Chile's two pre-World Cup warm-up matches were an indicator of the Barcelona attacker's importance to Jorge Sampaoli's team, and the clear and present danger he represents to the Socceroos.
Sanchez played a game and a half against Egypt and Northern Ireland. Chile scored five goals across the two games, all of which were set up by the 25-year-old.
How much does work does Ange Postecoglou, who is publically dimissive of focusing on individual opponents, put into Sanchez?
After an assist every 24 minutes, Sanchez would be giving the Socceroos' coaching staff plenty of headaches.
The manner of Sanchez's brilliance makes him one of the most dangerous individuals Australia will face in Brazil.
Spain have incredible individual quality but their best performances are based on fantastic team play.
The Netherlands have more predictable individual talent.
Jason Davidson knows what Arjen Robben will try to do, while Robin van Persie – under an injury cloud – is hard to stop but largely predictable.
Against lesser quality opposition in Egypt and Northern Ireland, Sanchez showed off his full array of skills.
Once against Egypt he made a 30-yard run down the right, keeping two defenders at bay, to set up a goal.
Then, he received the ball with his back to goal, turned and cut inside from the right before a wonderful chipped pass played Eduardo Vargas in.
The next goal was similar, but he played a pass from even deeper – just inside the attacking half – to set up Vargas.
Chile had looked short of ideas until Sanchez and Vargas came on against Northern Ireland.
The diagonal pass over the top to Vargas from Sanchez appears to be in Chile's playbook.
It opened the scoring against Michael O'Neill's side.
Sanchez played another defence-splitting pass for the second goal.
He cannot be allowed space, and several of his assists came from just inside Chile's attacking half.
Postecoglou wants his teams to focus on themselves, but Sanchez cannot be ignored.
Davidson cannot simply follow Sanchez because Juventus man Mauricio Isla enjoys making penetrating runs down the right as his team's wing back.
One of Mark Milligan or Mile Jedinak can be given the task when the former Udinese attacker drifts inside, but he can easily take advantage in the switch-over process.
As for man-marking, it would leave Sanchez creating space for the likes of Vargas and the fit-again Vidal.
But that may be the best option. Whatever they choose to do in an attempt to negate the Barca star, it won't be easy to excute.