Sanchez, who started the third-place game, limped off and appeared to be holding his hamstring.
It comes with the forward’s Old Trafford future in doubt after struggling in Manchester.
Sanchez joined United from Arsenal last January though has scored just five goals in all competitions.
And after seeing Sanchez leave the Copa America clash, some Manchester United fans want him gone now.
One posted: “He’s aware that the season kicks off soon…… What a wimp”
Another added: “This guy is just a Liability to this Team, can you imagine”
A third wrote: “Made of glass…get rid!”
While a fellow Red Devils fan posted: “When the time comes to roll up the sleeves and get stuck in Sanchez feels a strain. He shouldn’t be allowed near the first team.”
Sanchez had scored 80 times for Arsenal in 166 appearances but has not found the same form at United.
With his high wage, it’s led many to think Sanchez could be sold by Ole Gunnar Solskjaer.
And Sky Sports man Mark McAdam believes an Old Trafford exit might be best for the Chilean’s career.
McAdam said this week: “I feel sorry for him because I don’t want to see a footballer – particularly someone as talented as Alexis Sanchez – fail on the biggest stage.
“And that’s what’s happening at Manchester United.
“He was unreal at Arsenal. The amount of times I watched him drag that team towards three points…
“It just hasn’t worked out at Man Utd and I feel he deserves an opportunity to prove himself elsewhere.
“He has the quality. Players don’t become bad players overnight. He will go on to prove he’s a good player.”