Pep Guardiola has revealed that he decided to leave Riyad Mahrez out of Manchester City's Community Shield squad due to concerns he would fail a drugs test.
The Algeria winger had been keen to feature at Wembley, despite only returning to training on Friday after helping his country win the Africa Cup of Nations.
However, the City boss decided not to include the 28-year-old in his side for Sunday's penalty-shootout win over Liverpool after learning that he had taken medication during his time on international duty.
The club's medical staff were unable to determine the ingredients of the medication and didn't want to risk Mahrez falling foul of anti-doping rules.
“Riyad called me straight after being champion and said he wants to be back against Liverpool," said Guardiola after the victory. “I said he was more than welcome.
"But Riyad took some medicine just a little bit, but we don't know what he took and therefore doping control today was a risk because the doctors did not know what was in the medicine.
“So that's why he did not play today.
"He could have played some minutes, but we could not take a risk because the doctors didn't have the medicines.
"Hopefully at West Ham he will be fine.”
City beat Jurgen Klopp's side on penalties to secure the club's first piece of silverware of the season at Wembley.
Raheem Sterling got the defending Premier League champions off to a strong start with a first-half goal, but substitute Joel Matip levelled for the Reds after the break to ensure the match ended 1-1 after 90 minutes.
The encounter had to be settled by penalties, and City were able to seal victory as Guardiola's men successfully converted all five of their spot-kicks after Georginio Wijnaldum saw his attempt saved by Claudio Bravo.
