Jose Mourinho has been chasing Alexis Sanchez for more than a decade and tried to sign the Chilean twice during spells at Chelsea, according to the Manchester United manager's South American scout.

After being announced as a United player on Monday night, Sanchez trained with his new teammates for the first time on Tuesday and is in line to make his debut against Yeovil in the FA Cup fourth round on Friday night.

Jorge Alvial, who has worked as part of Mourinho's scouting team at Chelsea and United, has revealed it will be the culmination of a long pursuit.

"I recommended him since I arrived at Chelsea in 2006," the scout told La Tercera. "At the start he was very young, although obviously I saw him as one for the future.

"In 2013 during Jose's second spell at Chelsea, there was a lot of interest. It was between Chelsea and Barcelona, but he chose the Catalans for understandable reasons.

"[Mourinho] always liked him. What he admires the most about him is his leadership on the pitch, furthermore he is a player who can change a game in any moment owing to the great talent that he has."

Jose Mourinho tried to bring Alexis Sanchez, right, to Arsenal when he was Chelsea manager. Nick Potts/PA Wire/Press Association Images

In his first interview as a United player, Sanchez revealed he preference to play on the left or through the middle.

But it is on the right that Mourinho has struggled to find a regular starter and Alvial insists the 29-year-old is good enough to play anywhere -- including in tandem with striker Romelu Lukaku.

"This important investment was made because Alexis is a world-class player," Alvial told CDF News. "I'm not exaggerating, he is one of the best five players in the world. His performances in Arsenal left that clear. His work is very impressive.

"Alexis is a player that can help in any position. He is dangerous in all positions. He will be a multifunctional player for the attack above all because of the skills and quality he has.

"Mourinho has known him for several years. He had a detailed report on him when we worked at Chelsea.

"He is an exceptional player and he will fit in perfectly. He will complement the striker Romelu Lukaku. I am sure he will do well."