He forms the crux of our latest scouting report, where we analyse players' individual performances and explain what role they fulfilled.
Chile had a few injuries to deal with and, as a result, switched from a 3-4-3 to a 4-3-3 formation. The two are pretty interchangeable anyway, but it was the first time Jorge Sampaoli had played an orthodox back four for several months.
For a team like England that would have been a seismic shift, but for Chile—who have a team identity and common craft—the change was easy to adopt.
Throughout the game Eduardo Vargas, Eugenio Mena and Charles Aranguiz all trialed slightly different positions to the ones they adopted in qualifying, but others around them—including Sanchez—made it easy for them to adapt.
La Roja's base system is fluid, with counterattacks just as likely as possession football. It combines all the strengths Sanchez (a star player) has learned over the past three years, both with Udinese and Barcelona.
The team as a whole were incredibly comfortable playing out from the back, and Marcelo Diaz would often end up playing it to a wide forward who had dropped in to take the ball. Sanchez, playing on the right, was happy to oblige and help his teammates, then turn and use Mauricio Isla as a foil to steam forward.
His passing in tighter areas was good, he gave Leighton Baines a nightmare positionally and nipped in early at the back post to fire his nation ahead.
It was hardly a surprise to see Barca's second-top scorer for the season open his account in London, and he would go on to give the defence fits all evening.
Of the two methods Chile used to wear England out—slow possession football and rapier-like counters—it was the latter that suited Sanchez the most.
Claudio Bravo (GK)'s willingness to play in a Victor Valdes-esque manner forced England's forwards into pressing high up the pitch, but that wasn't part of the Roy Hodgson game plan. As he drew Wayne Rooney and Jack Wilshere in, holes began to appear in midfield, and the forwards would drop in to take advantage.
Two quick passes and Sanchez has room to turn in his own half, and that's where he can really do some damage.
Bravo laid a trap, and England fell into it; teams will have to be extremely careful of that at the World Cup, as Chile have the right set of players—Gary Medel, Diaz and Alexis/Vargas—to make this a lethal, cut-throat strategy.
Sanchez's second goal was reminiscent of the ones he would score at Udinese, as a late counter fed him in on goal from the flank, and his finishing did the rest. Since moving to La Liga, he has never been in better form, and England were unfortunate to run into him in his current groove.
If Chile play like this at the World Cup, they are the dark horses for victory. Alexis Sanchez could be very much among the goals.