The 23-year-old left Lazio for Turkish side Trabzonspor in August but alleges the Italians owe him two months’ wages.
Lazio had until 29 November to submit their response but now have an extra 10 days to state their case, says FIFA. Onazi’s representatives approached FIFA after Lazio failed to respond to their emails, fax and telephone calls.
Lazio had sought a 20-day extension to FIFA’s deadline, claiming they are struggling to translate written letters from Italian to English.
Onazi, who spent five years at Lazio and scored seven goals in 110 appearances, told BBC Sport: “It is unfortunate that the club chose this path.
“I believe in FIFA’s justice system to get my money from Lazio.”