Alexis Sanchez on said Monday he was “thrilled to be joining the biggest club in the world” as he moved to Manchester United from Arsenal in a swap deal with Henrikh Mkhitaryan.

The 29-year-old Chile striker, who came close to joining Manchester City last summer, has signed what is believed to be a four-and-a-half-year contract that will make him the highest-paid player in the Premier League.

It has been widely reported that Sanchez will earn a pre-tax salary of £500,000 ($695,000, €567,000) a week.

Armenia international winger Mkhitaryan, also 29, will head to the Emirates after he fell out of favour with United manager Jose Mourinho during 18 months at Old Trafford.

Sanchez joined Arsenal for £31.7 million in 2014 after three years at Barcelona but his relationship with the Gunners soured after he tried to orchestrate a move to City last year.

Hitting back at critics

In an Instagram post, Sanchez took a parting shot at ex-Arsenal players who have criticised his attitude.

“There are people (former club players) who have spoken with no knowledge of what happens inside the club and cause damage,” Sanchez wrote.

“I must say I always gave 100%, until the last day, when I asked to the Mister (Arsenal manager Arsene Wenger) to be in the team, because I wanted to be a contribution.”

Last week, former Arsenal defender Martin Keown called Sanchez “football’s biggest mercenary”.

In a statement issued by United, Sanchez said he had spent “three-and-a-half wonderful years” at Arsenal “and I bring with me very positive memories of that great club and its fans”.

Referring to Old Trafford, he said: “The chance to play in this historic stadium and to work with Jose Mourinho was something I could not turn down.

“I am very proud to be the first Chilean player ever to play for United’s first team and I hope I can show our fans all around the world why the club wanted to bring me here.”

Investment on Sanchez is significant

United will be hoping their substantial investment helps close the gap on their Emirati-backed cross-city rivals Manchester City, who are streaking away with the Premier League title this season.

Sanchez will partner Romelu Lukaku in the United forward line, with England strikers Marcus Rashford, 20, and the in-form Jesse Lingard, 25, forced to fight for their places.

Mourinho said: “Alexis is one of the best attacking players in the world and he will complete our very young and talented group of attacking players.”

Sanchez spent three years at Barcelona, winning La Liga in 2013. At Arsenal he twice lifted the FA Cup, but did not come close to a Premier League title and his frustration has been evident this season amid reports of rows with teammates.

He has played 119 times for Chile and helped his nation win back-to-back Copa America titles in 2015 and 2016, although they failed to qualify for next year’s World Cup in Russia.

His move to United was celebrated in his homeland, where fans on social media lauded the Red Devils’ “winning” mentality, in contrast to the paucity of recent success at Arsenal.

“The golden destiny of Alexis,” said daily newspaper La Tercera.

Mkhitaryan joined United for around £30 million in 2016 after three years at Borussia Dortmund.

The highlight of his stay in Manchester was scoring in the Europa League final victory over Ajax last season and he also helped United win the League Cup.

“I would like to wish Henrikh all the success and happiness that I am sure he is going to get. He is a player that we will not forget, especially for his contribution to our Europa League victory,” added Mourinho.

Mkhitaryan told the Arsenal website he had “always dreamed of playing for Arsenal”.

“Now that I’m here, I’ll do my best for this club to create history,” he said.

Arsenal boss Wenger said he was happy to acquire Mkhitaryan in the deal.

“Henrikh is a very complete player. He creates chances, he defends well, he can absorb distances and he’s very committed as well.

“I must say he’s a player who has all the attributes.”

The Sanchez-Mkhitaryan deal is the latest move of a January transfer window during which Liverpool sold Philippe Coutinho to Barcelona for €160 million and signed central defender Virgil Van Dijk from Southampton for £75 million (€85.5 million).

Reports in Germany say striker Pierre-Emerick Aubameyang could be on his way to Arsenal from Borussia Dortmund.

Henrikh Mkhitaryan will have his work cut out to reverse Arsenal’s flagging fortunes, after joining the Gunners from Manchester United on Monday in a swap deal that saw Alexis Sanchez move in the opposite direction.

The 29-year-old had a difficult spell under Jose Mourinho at Old Trafford, but Arsenal manager Arsene Wenger will be hoping the Armenian can rediscover the form he showed at Borussia Dortmund that led to him signing for United for a around £30 million in 2016.

Will Mkhitaryan get a starting place?

Mkhitaryan struggled to nail down a spot in United’s team despite arriving from Dortmund with an excellent reputation after three strong seasons in Germany that produced 27 goals and 34 assists in all competitions.

Sanchez’s departure leaves Mesut Ozil as Arsenal’s creator-in-chief. Aaron Ramsey and Jack Wilshere have both been plagued by injuries in recent years, while Alex Iwobi has failed to consistently impress despite being given a lengthy run in the side. Mkhitaryan looks set to slot in alongside Ozil and behind striker Alexandre Lacazette if he finds anything like the form he showed in the Bundesliga and before that with Shakhtar Donetsk.

Is he a replacement for Sanchez?

Although Mkhitaryan is moving to London in a switch with Sanchez, he is not a direct replacement for the Chilean international. Sanchez provided ruthlessness in front of goal and the ability to run at defenders, while Mkhitaryan’s strengths lie with his passing and creativity. Sanchez has scored 60 Premier League goals in 122 appearances, while Mkhitaryan managed just five in 26 games at United.

But the Armenian leads Sanchez in other areas, making more assists and passes per game. Mkhitaryan completes 51.47 passes a match compared to Sanchez’s 48.16 according to statisticians Opta, suggesting his style of play will fit in with Wenger’s preference for passing football. Mkhitaryan does have more goals in him too, having scored 23 in 78 Bundesliga appearances before finding himself deployed in a variety of positions by Mourinho at United.

Do Arsenal need another attacking midfielder?

Wenger has been criticised in recent years for buying too many attack-minded midfielders and ignoring other supposed weaker spots in his team. With close-season signing Alexandre Lacazette struggling to find the net with regularity – he scored his first league goal since December 2 in Saturday’s win over Crystal Palace – Wenger will be hoping Mkhitaryan can bring the best from the French striker. The 68-year-old Frenchman is confident he can start Mkhitaryan with the likes of Ozil, Ramsey and Wilshere. “Just play the good players, they can always play together,” he said.

Wenger has always favoured selfless players, and Mkhitaryan fits that mould. “He managed to build his relations with the team-mates in a way that allows him authority on and off the pitch,” former Shakhtar coach Mircea Lucescu told the Guardian in 2012. “Working with him is fun. He’s a complete player.”

Can he help Arsenal return to the Champions League?

Arsenal fans expect their team to be challenging for the Premier League title, but the stark reality suggests that they are some way from matching Manchester City and even United. Just returning to the Champions League after missing out this year for the first time since 1998 is still a formidable task, with Arsenal currently lying sixth.

If Mkhitaryan can quickly strike up a relationship with Lacazette and Ozil then Arsenal could start to close the gap, but they are probably still another top signing away from challenging for the biggest titles. Mkhitaryan’s former Dortmund team-mate Pierre-Emerick Aubameyang has also been heavily linked with a move to north London, though, and perhaps reuniting the pair could prove to be exactly what Arsenal need to close the gap on the rest of England’s ‘big six’.