In 2018, he moved to league rivals Manchester United in a swap deal; he signed for Inter Milan a year later, and won a Serie A title and a Coppa Italia.

[20] Sánchez debuted for Colo-Colo on 23 June 2006 in a 1–1 draw with Antofagasta; he scored his first goal on 29 October during the Chilean football derby against Universidad de Chile in a 4–2 win.

[21] His good performances allowed him to break into the starting lineup after successfully challenging veteran striker Mario Cáceres, and he then began partnering Humberto Suazo in the forward position.

[26] On 12 May, Sánchez scored his first and only one league goal during a 3–1 home win over Santiago Wanderers,[27] key in the race for title with Universidad Católica which Colo-Colo finally reached after beat Palestino 1–0 at Monumental the last matchday.

[29] After a successful season in Argentina, Sánchez left South America in July 2008 to join Udinese, where he would meet up with Chilean compatriot Mauricio Isla.

[citation needed] The next season, Sánchez played an important role for Udinese in the Coppa Italia, being a key player in the team that eliminated Milan, assisting Gökhan Inler for the winning goal.

[31] In the semi-final second leg, Sánchez was the man of match after playing a successful game against Roma, including scoring his first Coppa Italia goal in the 81st minute.

[37][38][39] "Sánchez is very young", said then-manager Pep Guardiola; "He can play in all three attacking positions, he shows intense defensive skills, he's direct and from what I've been told, he's a very nice kid.

He made his debut on 14 August 2011 against archrivals Real Madrid in the 2011 Supercopa de España first leg away match, suffering a thigh injury after a challenge by Marcelo.

[44] From February onwards, Sánchez scored in matches against Deportivo de La Coruña, Mallorca, Athletic Bilbao, Real Betis, Atlético Madrid and Espanyol to end the season with eight league goals.

On 26 October 2013, Sánchez scored the winning goal as Barça beat Real Madrid 2–1 at Camp Nou in the first Clásico fixture of the 2013–14 La Liga season.

[50] Manager Arsène Wenger praised Sánchez, saying that the Chilean international "has consistently produced top-quality performances at the highest level for a number of seasons now and we are all excited to see him integrate into the Arsenal squad".

[55] He then scored his first goal for Arsenal on 27 August, slotting the ball past Beşiktaş goalkeeper Tolga Zengin in stoppage time of the first half to secure a 1–0 aggregate victory and a spot in the group stage of the 2014–15 Champions League.

[57] He then scored his second league goal in as many games against previous season champions Manchester City, demonstrating perfect technique to sidefoot a volley high past goalkeeper Joe Hart in a 2–2 draw at the Emirates Stadium.

The following league fixture saw him scoring a brace against Sunderland after capitalising on errors made by defender Wes Brown and former Arsenal goalkeeper Vito Mannone.

[65] On 4 January 2015, Sánchez scored and assisted his first ever FA Cup goals as Arsenal knocked out Hull City, the previous season's runners-up in the third round.

Sánchez, who also headed an assist for Theo Walcott's opening goal, became the first Chilean to score in an FA Cup final since Newcastle United's George Robledo in 1952.

The following week, on his first start of the season, Sánchez had a header deflected into the Crystal Palace net by Damien Delaney to give Arsenal a 2–1 win at Selhurst Park.

[80] Following a brief period on the sidelines due to injury, Sánchez returned to full first-team action on 30 January 2016 in the FA Cup fourth round tie against Burnley, scoring Arsenal's second goal of the game following a low cross from Alex Oxlade-Chamberlain.

[85] Sánchez scored his first Champions League goal of the campaign in a 1–1 draw with Paris Saint-Germain on 13 September 2016, latching onto Alex Iwobi's rebounded shot, to secure Arsenal a point in the French capital.

[91] On 22 January 2017, Sánchez scored his first penalty for the club (having missed his previous two) against Burnley in an eventual 2–1 win, which put Arsenal into second place in the Premier League table.

[99] But throughout the transfer window, there was increasing speculation about his future, with a huge amount of reports stating his desire to leave, in order to play in the Champions League.

[103] Sánchez scored his first Premier League goal of the season in a 5–2 win over Everton and he also provided an assist for Mesut Özil to put Arsenal ahead.

On 15 November 2013, Sánchez scored both goals as Chile beat England 2–0 at Wembley, repeating the achievement of national team legend Marcelo Salas in 1998.

On 14 June, needing a draw to progress to the knockout rounds, Chile fell 1–0 behind to Panama before both Sánchez and Eduardo Vargas scored twice in a 4–2 win in Philadelphia to qualify for the tournament quarter-finals.

[147] On 22 June 2017, Sánchez became Chile's out-right all-time goalscorer when he scored the opening goal in an eventual 1–1 draw against reigning World Cup champions Germany in his team's second group match of the tournament, overtaking Marcelo Salas with his 38th international goal in 112 appearances, and also equalling Claudio Bravo as his nation's joint top appearance holder in the process.

[148][149] Chile defeated Portugal on penalties in the semi-final, before losing 0–1 in the final against Germany, with Sánchez coming close to an equaliser with his injury time free kick saved by German goalkeeper Marc-André ter Stegen.

[152] In the quarter-finals against Colombia on 28 June, following a 0–0 draw after regulation time, he scored the winning penalty in the resulting shoot-out to send Chile to the semi-finals of the competition.

[159][160][161][162][163] A talented forward, Sánchez is gifted with excellent dribbling skills, flair, finishing, vision and acceleration, which enables him to successfully take on opponents with feints in one on one situations, create space, and either score goals himself or set-up his teammates from through balls, long-range passes, or one-twos.

[172] In June 2022, he announced the purchase of land in Mendoza in Argentina, Maule Region in Chile and Friuli in Italy for his undertaking called Alma Soul, focused in the wine production.