The rant comes after a disappointing week for Sanchez and the Chilean national side saw them lose both their World Cup qualifiers, falling to a 3-0 defeat to Paraguay on Thursday before being edged out 1-0 by Bolivia earlier this week.
The results leave Chile in sixth place in the South American World Cup qualifying group, with the top four going to next summer's tournament automatically and the fifth placed team facing a play-off.
Now Sulantay, who is currently the coach of second division side Cobreola, has hit out at the nation's poster boy.
In an interview with Chilean publication 'La Cuarta', the former Chile U20 coach said: 'I saw him (Sanchez) gone, I saw him out of physical shape, totally. He's fatter than normal.
'Without his spark, he never left that Paraguayan defence behind. He never made a diagonal run, it was something else. It was not Alexis.
'This can bring you problems later, the statements of wanting to leave. The team-mates must have felt nothing for him.'
Given that the Paraguay game took place on transfer deadline day it is very possible that the player's mind was elsewhere but that does not excuse his performance in the eyes of Sulantay.