World champion Ronnie O'Sullivan has withdrawn from the Championship League because he does not want to stay in isolation at the event.
The tournament is taking place in a bubble environment at the Marshall Arena in Milton Keynes.
Its format sees players in groups of four so would require further isolation if O'Sullivan progressed to the latter stages, which he is not willing to do.
O'Sullivan, 44, was in a group with Li Hang, Alex Borg and Iulian Boiko.
His place will now go to John Astley.
O'Sullivan's spot had been offered to Lei Peifan - who was next on the Q School order of merit - but the Chinese player decided to leave the event after returning an invalid test result followed by a negative one.
In June, O'Sullivan admitted he had struggled inside the bubble in place at the same tournament and the same venue.
"If every tournament was to be like this then I am not sure I would be able to do it," he said at the time.
"I like my own company but it is tough being cooped up. It is not easy for me, I must admit. It is just about having the freedom to go out for a walk, get a bit of fresh air and a coffee."