Benjamin Evans, 18, of Erw Wen, in Morda, near Oswestry, admitted causing grievous bodily harm to the teenager on August 24.
Prosecuting at Shrewsbury Crown Court, Jason Pegg said the teenager's head injury was "consistent with being knelt on during the course of a confrontation".
Evans denied another count of intentionally causing grievous bodily harm.
Representing Evans, Andrew Green applied for the case to be adjourned so a pre-sentence report can be carried out.
Judge Anthony Lowe agreed said: "Although your plea has been accepted it is a serious matter. Any physical confrontation that results in someone having a bleed on the brain is bound to be considered serious by the court."
He adjourned the case to August 5.