A nasty kick to the head left a Socceroos star bloodied as Australia battled Paraguay in a tense World Cup crunch clash that had everything on the line.

With a place in the knockout stage hanging in the balance, the match stopped for several minutes when a Paraguayan boot caught Connor Metcalfe high in the head during a desperate challenge in the first half.

As the star midfielder hit the ground, a Paraguayan opponent’s boot accidentally smashed into his face, leaving Metcalfe clutching his head in agony.

His teammates immediately rushed to his aid, with replays showing blood streaming from a deep cut as medical staff came to is aid.

The blow stunned fans and players alike, with the Australian left visibly shaken before receiving lengthy treatment.

Metcalfe’s head was heavily bandaged when he returned to the field.

“That would definitely hurt,” Socceroos great Luke Wilkshire said on SBS.

“He got him good. He’ll have a black eye in the morning.”