Alexis Sanchez faces up to two months on the sidelines according to Chile national team doctor Pedro Onate, who analysed the knee injury the forward sustained in Manchester United's win over Southampton.
Sanchez was replaced after 52 minutes of the 3-2 victory at Old Trafford following a challenge from Saints defender Jan Bednarek and United's own medical staff have yet to provide a prognosis.
But Onate said that exams of Sanchez's condition showed he had suffered distention of the medial ligament, which would take a number of weeks to heal.
Onate told El Mercurio: "There won't be any problems for him to be at the Copa [America], because he'll be out for between six and eight weeks.
"Alexis may even play again before that time. Plus, there's a long way to go until the Copa America.
Ole has provided the latest on @Alexis_Sanchez... #MUFC
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"The distention of the medial ligament is an annoying injury, but it's not so complex."
United will be without Sanchez as they travel to Paris Saint-Germain for the second leg of their Champions League last-16 tie on Wednesday, where they hope to overturn a 2-0 deficit.
Sanchez has made just eight Premier League starts for the club in 2018-19, scoring once.
The 30-year-old winger has endured a difficult period at Old Trafford since arriving from Arsenal in January 2018, struggling to live up to expectations and suffering a worrying loss of form in front of goal.
Five goals from 41 appearances across all competitions are not the kind of numbers English football fans have come to expect from Sanchez, who became one of the Premier League's most revered players during his four-year spell at the Emirates Stadium.
In his absence, caretaker boss Ole Gunnar Solskjaer may be forced to play a flat 4-4-2 formation against PSG, with Fred and Andreas Pereira in line to start.
