UEFA insists refs must 'protect' players

"We need to have players playing, so they must be protected on the field," said the Italian. 

"We do not want situations where a player's future is put in doubt because of serious injury caused by a challenge, whether it is intentional, or is unintentional and the player making the challenge is taking a risk of causing injury," he went on to add.

Man City manager Pep Guardiola has been outspoken on the treatment of his players in past weeks, claiming they are subject to fouling that puts them at risk and calling for more serious action to be taken. 

Collina has also asked referees to be strict with "professional fouls," which serve to intentionally stop a team breaking away and creating a goal-scoring opportunity, and "mobbing."

"When I see mobbing of a referee, it's something that is not acceptable - this is not the message that we want the game to convey," he said.

With City taking on Basel in the Champions League on Tuesday night, it will be interesting to see how officials react to hard challenges on Guardiola's men.