Xavi, who renewed his contract with the Qatari club on July 5, said he would go on to self-isolate as his team prepare for their first match on Saturday.
The Qatar Stars League (QSL) would be restarting after it was suspended due to the COVID-19 pandemic.
“Today I won’t be able to join my team on their comeback to the official competition,” Xavi said in a statement.
“David Prats, coach to the Al-Sadd reserves, will be there on my behalf as head of the technical staff.
“A few days ago, following 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.”
The QSL resumed on Friday after being suspended since March due to the new coronavirus pandemic.
Al-Sadd, who are third in the table, play Al-Khor on Saturday with five rounds remaining.