The 28-year-old last month helped Algeria to the Africa Cup of Nations title and Guardiola said the club did not have all the information as to the treatment Mahrez might have received.

"Riyad called me and said, 'I want to play against Liverpool'. I said, 'You are more than welcome'. But we don't have what he took... about the medicine," said Guardiola.

"That's why, for doping control, today was a risk because the doctors didn't have it. He could have played some minutes but we could not take a risk because the doctors did not have exactly the medicines.

"Hopefully he will be back next game against West Ham and in the future everything will be normal."