The capture should see the Gunners challenge for the title next season. However, if truth be told, the most significant signing the club has made in recent years was on May 30 when Arsene Wenger signed a new long-term contract.
Le Prof signing on the dotted line is the main reason Sanchez joined Arsenal. The Frenchman now stands as a lone paragon of virtue in a footballing world obsessed with athleticism over technical ability.
If this World Cup has taught us anything, it has shown us that world football is in decline.
The Brazil-based tournament produced an excellent group phase where the perceived gaps between the haves and have-nots of world football shortened dramatically. However, as soon as the knockout stages began, it became obvious to all that technical ability is now less in demand than athleticism.
The game and, as such, coaches are not producing players and specifically midfielders as they did in years gone by. Of all the nations at the World Cup, only Germany can boast having a midfield worth talking about.
Brazil, a nation of more than 200 million people, the fifth-highest population in the world and twice the population of northern Europe, have not produced a world-class central midfielder in years. Andrea Pirlo stands alone in Italy at 35 years of age, Spain are over-reliant on the 34-year-old Xavi Hernandez and England have no one.
There is a massive difference between athletes who are footballers and footballers who are athletes.
The current trend in football shows us that limited central midfielders, such as France's Blaise Matuidi, are now seen as the template to follow. Matuidi powered his way through Ligue 1 and to the French title last season with Paris Saint-Germain FC. He also trampled upon everything placed in front of him during the group stage at the World Cup.
However, when questions were asked of him by Germany, he was unable to answer. His limited technical ability and poor passing vision were exposed as France crashed out of the World Cup without threatening the Germans at all.
This is where Arsenal are unique in English football and practically so in world football.
The single most important thing for any central midfielder, be he on Hackney Marshes or playing in the Maracana, is that he has to move toward the ball to receive it whilst also moving into space.
One of the first things you learn playing football is to provide angles to receive the ball. In an ideal world, the player on the ball will have three options at least. Two will be to the side to offer width while one will offer penetration down the middle.
The four players will form a rough diamond shape, and as the ball moves on, this diamond will reform depending upon the situation. Think Barcelona and all those little triangles they always seem to find.
This is football at its most basic. It is learned on the street avoiding broken bottles, parked cars, bullies twice your age and lampposts. This is where ingenuity and imagination take hold, where cleverness beats physicality every time. Here, players learn guile, art, craft and become unafraid of receiving the ball.
One would almost have to wonder if it is coached out of players these days.
There is an unwritten rule in the English Premier League and now it seems in international football that a midfielder will not take responsibility and receive the ball if an opponent is within three to four yards of him.
The exceptions to the rule are almost every Arsenal midfielder and but a few brave men such as Luka Modric, Pirlo and Xavi.
Aaron Ramsey, Jack Wilshere, Alex Oxlade-Chamberlain and Mesut Ozil are supremely gifted footballers and possess enough technical qualities to have played for any team at the World Cup, with the exception of Roy Hodgson's England for some bizarre reason in the case of Wilshere and the Ox.
Here the importance of Wenger becomes apparent.
Wenger allows his players to evolve naturally but most importantly in the way the game was meant to be played.
This style, coaching ability and philosophy is the main reason Sanchez joined Arsenal. Upon joining the Gunners, he said, as per the club's official website:
Arsenal plays very well, which fits my style. That is why I moved here.
Arsene Wenger's style of play is the sort of style the Chilean national team has, so therefore I am used to it.
I know this club has a manager that looks after his players and takes care of them as well. I was told that he is a manager you can learn a lot with. He wants to achieve great things in football and that helped me make the decision to sign for Arsenal.
With [Mesut] Ozil in the squad Arsenal was [close] to winning the league title [last season]. I hope I can make a contribution so we can win as many titles as possible.
We have a great squad and we are a big club. We can achieve big things. I came here to win the league title, the Champions League and every title at stake.
Sanchez fits right into Wenger's philosophy. Wenger likes highly mobile, highly technical players who are interchangeable in the final third of the pitch.
Ideally, you want to have a player who has everything.
Our game at Arsenal is based on technique and movement – that means I look at the pace of the player and his technical level.
These elements don't always go with power or physical commitment, but we want our game to be very mobile and very fast, therefore we need a good technique and to be able to move quickly.
Of course, you want power and physical presence, but the priorities for me are pace and technique.
This can be easily seen in the development of youth players and the overall philosophy at Arsenal football club.
The passing game employed by Wenger's teams has often been described like a dissection by a master surgeon. His teams rip the opposition apart through rapier-like movement off the ball combined with technique, a superb first touch and great vision on the ball.
Top-level football is all about utilizing space, specifically the small spaces available near the opponents and the larger spaces behind the defense.
Arsenal have highly mobile and technical players all over the pitch and control this space jealously. They are more than capable of adapting to any opponent but have suffered through inexperience, injuries and at times a more physical approach.
Arsenal's philosophy, partly developed by Alfred Galustian and Coerver coaching, has seen the club concentrate on the technical ability of players 14 and under. After this age, the club introduces mobility, speed exercises and works on enhancing in-game intelligence.
Where all this pays off is in Arsenal's great creation and development of highly technical players over the years and in the improvement of players such as Thierry Henry, Patrick Vieira and even Dennis Bergkamp to name but a few.
Quite simply, Arsene Wenger is recognized as the top coach and manager in world football for developing players. For years this reputation was not enough alone. Ten years without a trophy is a long time in any man's language.
However, Arsenal's FA Cup win over Hull City has reignited their sterling reputation amongst top-class players, regardless of Wenger's phenomenal record at qualifying his club for the Champions League.
Sanchez's signing on top of Ozil's from last season stands out because they are two of the world's best players. It has been a long, long time since the Gunners were able to attract players of this nature and class.
Arsenal are now being linked with another recognized star in Real Madrid's Sami Khedira, according to Jeremy Wilson in The Telegraph, as Le Prof looks to build upon last season's success. Khedira has long been linked with Arsenal and would link up with fellow countrymen Ozil, Per Mertesacker, Lukas Podolski and Serge Gnabry should he commit to the upcoming Arsenal revolution.
Back in May, when signing the likes of Sanchez and Sami Khedira was but a dream to Arsenal fans, Wenger told the club's website:
I want to stay and to continue to develop the team and the club. We are entering a very exciting period. We have a strong squad, financial stability and huge support around the world.
We are all determined to bring more success to this club.
The club has always shown faith in me and I'm very grateful for that. We have gone through fantastic periods and also periods where we have had to stick together. Every time when that togetherness was tested I got the right response.
Hopefully we can make some more history. I am sure we can.
It has been a long time since Wenger joined Arsenal and banned Mars bars. Since then Wenger has led Arsenal to three league titles, five FA Cups and four Charity/Community Shields, including two league and cup doubles in 1998 and 2002.
He is the only Arsenal manager to have won the FA Cup more than once and the only manager to take the club to a European Cup/Champions League final.
He is also the first manager in English league history to complete an entire 38-match season unbeaten.
Along the way he has developed some of the greatest players of the modern age.
Captures such as Ozil and Sanchez will quite rightly excite the fans, but the reason they sign is to learn under Wenger.
The fact that these players are joining as they near their peak is more than encouraging where titles are concerned, and it's all down to Le Prof.