The former Barcelona star says he is "feeling OK" but is self-isolating as per competition protocols.
In a statement released via the club's website, the Spain great said: "Today I won't be able to join my team on their comeback to the official competition.
"A few days ago, [after] the QSL protocol, I tested positive in the last COVID-19 test. Fortunately, I'm feeling OK, but I will be isolated until I am given the all-clear.
"When the health services allow it, I will be very eager to return to my daily routine and to work.
"I'd like to thank all the authorities, especially those working in QSL, QFA [Qatar Football Association] and Al Sadd for supplying the means of early detection, reducing the spread of infection and that guarantees the normal development of the competition.
"Take care and see you soon on the football pitch!"
Reserve team coach David Prats will take charge for the match, Al Sadd's first since the league was suspended in May.