The Chilean forward ended his three-and-a-half-year spell with the Gunners after swapping places with Henrikh Mkhitaryan, who moved to their new homes of Old Trafford and the Emirates Stadium respectively.
Official confirmation of Pierre-Emerick Aubameyang’s club-record £55million transfer to north London will also boost Gunners fans who are feeling low, following their 3-1 defeat to Swansea on Tuesday night.
Arsenal fans may be feeling a sense of déjà vu as they watch another of their star players head for Old Trafford, as Robin van Persie did back in 2012.
But with a new attacking quartet of Aubameyang, Mkhitaryan, Alexandre Lacazette and Mesut Ozil to look forward to, supporters of the Gunners could be feeling more positive about the future.
Here talkSPORT gather the evidence and attempt to convince Arsenal fans why waving goodbye to Sanchez is not the disaster they fear it to be.
Value for money
Placing valuations on players is a tricky task in the modern era thanks to the sky-rocketing of transfer fees in the last year, particularly.
Arsenal found themselves in the unenviable position of possessing an undoubtedly world class player with only six months remaining on his contract. Sanchez, given his suitability to the Premier League, was able to command a hefty fee regardless of his situation.
Mkhitaryan joined United for a reported fee of £30million back in 2016 but has since failed to make an impression at Old Trafford under Jose Mourinho.
The Armenian is joined by the £55m signing of Aubameyang from Borussia Dortmund, taking the pair’s combined transfer fee to £85m effectively.
Gaining two established performers on the right side of 30 for a player who has stated his desire to leave the club appears to be a sensible option, but it is the Gunners who are paying the price.
Although Sanchez’s departure has caused upset, Arsenal fans should be excited about the reunion of Aubameyang and Mkhitaryan.
The pair spent three seasons together in Dortmund where they collected the German Super Cup and struck up a partnership that lit up European football in the 2015/16 season.
Dortmund finished behind eventual champions Bayern Munich, but Aubameyang and Mkhitaryan were both included in the Bundesliga team of the season – the only two players outside of Bayern to be listed.
Aubameyang went on to score 39 goals in all competitions in a season which culminated in him winning the Bundesliga Player of the Year Award.
The Gabon international’s achievements would not have been possible without the contribution of Mkhitaryan, who enjoyed a stunning season that saw him end with 23 goals and 32 assists to his name.
Mkhitaryan’s form captured the attention of Manchester United and Jose Mourinho, who saw off a host of interested clubs to seal one of the transfer coups of that summer.
A return of five goals and six assists over the course of one-and-a-half Premier League seasons clearly is short of what the Red Devils would have expected.
But with a new environment and some familiar faces, Mkhitaryan could finally show his undoubted talent at the Emirates Stadium.
Alexandre Lacazette factor
One of the biggest disappointments of Arsenal’s season has been the impact of summer signing Alexandre Lacazette.
The French international arrived with considerable pedigree having scored 100 goals in 203 Ligue 1 appearances.
But things have not gone as smoothly as the 26-year-old would have wished. Lacazette has managed a paltry nine goal return in the Premier League across 25 appearances, and endured an eight-game domestic barren spell before scoring against Crystal Palace.
Lacazette has been deployed as a lone striker in the main and has often seen his efforts ignored when making darting runs behind opposition defences. This event could be thanks to his teammates being selfish or simply not being on the same wavelength.
Sanchez’s departure opens up a place in Arsenal’s three-man attack, which previously saw Lacazette line-up alongside Sanchez and Mesut Ozil.
This season has seen Sanchez score seven goals in the Premier League – a low tally by his standards – and has drawn criticism from fans and pundits alike for his apparent displays of frustration on the pitch and lack of effort.
But with the arrivals of Aubameyang and Mkhitaryan, Lacazette can expect to see his role take on a new purpose in a revamped starting XI.
Wenger could decide to play Aubameyang and Lacazette together as a front two with Ozil and Mkhitaryan in support.
The potential results of those four playing together could see the Gunners put in a much improved performance in the second half of the season.
And should the attacking experiment pay off, Arsene Wenger will be able to justify the extra £55m outlay if it means getting the best out of Lacazette and his forward options.