After taking a dangerous-looking knee to the head, Uruguay's Alvaro Pereira laid motionless on the pitch in Sao Paulo during the second half of a World Cup match against England.

Pereira appeared knocked out, possibly concussed, before he was gingerly helped off the field by the Uruguay trainers. On the sideline, cameras showed Pereira visibly upset when he was advised not to return to the match. 

Pereira won out in the end and continued playing as Uruguay nursed a 1-0 lead.

Had this been a hockey game, Pereira might still be sitting in the quiet room. It's obviously a bit different in soccer.