Top newspapers revelled in the fact that Alexis' move to the Red Devils, on a reported 500,000 pounds (USD 695,000, 567,000 euros) weekly pre-tax pay packet, makes him the best- paid Chilean footballer in history.
"The Enviable Gold of Alexis" headlined La Tercera, trumpeting that the 29-year-old "has become the best paid Chilean player in history, with the highest salary in the Premier League and the fourth highest in the world."
"Yep, Red definitely suits you," said Chile's Football Association in a tweet. Chile's national side are known as "La Roja" -- the Red.
United will be Alexis' fourth European club, after Udinese, Barcelona and Arsenal.
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A native of Tocopilla, a northern desert town of the shores of the Pacific, Alexis began his career playing for Corbreloa, from the Atacama desert mining city of Calama.
Italian club Udinese snapped up the 17-year-old after just one season.
The striker said on Monday that he could not turn down the chance to work with United manager Jose Mourinho.
La Tercera said Alexis had become a "collector of top bosses" having also played under the Argentine Marcelo Bielsa in the Chilean national team, Diego Simeone -- while on loan to River Plate -- and Pep Guardiola at Barcelona.
"City play one- and two-touch football and the players have to stick with that, often hiding the real talent they have. United play more direct, so the power, technique and speed of Alexis will be very positive for Mourinho's team," Sulantay told El Mercurio.
Along with players like Bayern Munich's Arturo Vidal, Alexis is part of the so-called "Golden Generation" of Chilean football who failed to qualify for this year's World Cup.