The striker has sealed his move from Universidad de Chile and arrives with a reputation for hitting the net on a regular basis. After being across Sir Alex's radar for some time, the 18-year-old will train with the first team but is likely to be used initially at Reserves or Under-21 level.
Speaking before the third-round draw pitted the Reds with Newcastle, the boss also suggested Henriquez could feature in this season's Capital One Cup but it's clear the new No21 will be monitored carefully at Carrington.
"We scouted him when he was 14 years old and just monitored him," Sir Alex told Inside United. "When he turned 18, we knew we could take him; it's the first time we can sign them in this country, at 18, and so we were very fortunate the Chile Under-20s were over here.
"They were in tournaments at the Milk Cup [in Northern Ireland] and over in Holland.
"Chile Under-20s were in tournaments at the Milk Cup and over in Holland. We watched all the games and everyone said: 'You need to bring him in'."
- Sir Alex Ferguson, Inside United