After arriving at Carrington, Stoke’s players and staff found out their Covid-19 results which were taken in tests on Monday ahead of the Championship’s return.
Stoke officials immediately told United, who called off the friendly.
Stoke’s statement on the matter read: “Stoke City can confirm that manager Michael O’Neill has tested positive for the Covid-19 Virus following the latest round of testing on Monday June 8.
“O’Neill had tested negative in the previous five rounds of testing.
“He will now follow the relevant guidance and undergo a period of isolation, whilst continuing to be in regular virtual contact with his coaching staff and players.
“Assistant manager Billy McKinlay will take charge of training as the Potters prepare for their game against Reading on June 20.