He began his professional career with the Chilean club Cobreloa. He played one season there before being signed by the Serie A team, Udinese. Udinese had to pay nearly $3 million for his signature. Colo-Colo then paid Udinese nearly $150,000 for his services in the upcoming Clausura tournament and the following Apertura tournament in the Liga Chilena.
He scored his first goal with Colo-Colo in the Copa Sudamericana 2006 against the Liga Deportiva Alajuelense on October 10, 2006 in David Arellano Stadium.
On March 12th 2007 Sánchez hurt his toe and there were major fears that Sánchez's career may be over.
On March 20th 2007, Sánchez made a miraculous recovery from his bad toe and scored a hat-trick in a Copa Libertadores group match versus Caracas.
On August 15th 2007, he was signed to River Plate on loan. Udinese has Alexis Sanchez valued at 20 million euros.
On June 18th 2008 newspaper reports were published linking Sanchez to a move to Manchester United FC. Sanchez the 'Wonder Boy' is dubbed the next 'Cristiano Ronaldo'.
At the young age of seventeen, Sánchez has played for the Chilean National team on several different occasions. He debuted when the international team took on Universidad Católica. He played in a friendly game against New Zealand in Chile.
Prior to the 2006 FIFA World Cup in Germany, the Chilean National Team went on a tour in Europe playing three friendlies. They played Ireland, Côte d'Ivoire, and Sweden. Sánchez played significant minutes in all three games impressing scouts.
Despite only scoring one goal in the 2007 South American Youth Championship, Sánchez proved to be a vital part of the...