Michael Obi was released by his abductors on Monday and police said two Nigerian military officers were part of the group who took him on August 12.
"[The kidnappers] asked him to give them $4 billion which they called chicken change to Mikel Obi and his club Chelsea," police state commissioner Emmanuel Dipe Ayeni told reporters in Jos, capital of central Nigeria's Plateau state.
He did not say whether any ransom was paid.
Mikel earns $5.8 million a year and is the seventh highest-paid African footballer in Europe, according to Forbes magazine.
The Nigeria midfielder played for Chelsea in a 0-0 Premier League draw at Stoke City the day after learning of the kidnapping and made public appeals for his dad's safe return. His management company said at the time a "sizeable" ransom had been demanded.
It was not the first time a relative of a Premier League player was abducted in Nigeria, where most people live on less than $2 a day, after former Everton defender Joseph Yobo's brother was kidnapped in 2008.
Kidnapping of oil workers in the southern Niger Delta has been relatively common in the past but abductions have begun spreading further north.
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