Mikel’s father, Michael, was seized on Friday but the player insisted on playing in his club’s Premier League opener.
Mikel’s representatives, Sport Entertainment and Media Group, said: “Thus far no ransom (demand) has been received.
“Mikel was informed by his manager prior to the Stoke v Chelsea match and decided to play so as not to let down his team and family.”
Michael Obi, who runs a transport company, has not been seen or heard from since he failed to return home from work in Jos, the capital of Plateau State in central Nigeria.
Mikel’s agent, John Ola Shittu praised his client for the character he showed in turning out against Stoke.
“He is totally devastated. We were not sure whether to tell him before the game,” he said.
“But after speaking to the manager and Mike Emenalo (Chelsea’s sporting director) we agreed that he had a right to be informed of such a serious incident.
“He was under a lot of stress but he showed a lot of character and mental strength to play against Stoke.”
The abduction comes after a Forbes magazine survey in June named Mikel as the seventh highest-paid African player in Europe, with a salary of $5.8 million (€4m) a year.
Shittu told the BBC: “It’s been tough for the young man.
“The family in Jos reported him missing at the police station as expected but we’re taking all necessary measures to find him.
“We’ve told him to be brave and to stay calm.”
Mikel is not the first Premier League player to have a family member abducted in Nigeria.
In July 2008 the elder brother of Everton defender Joseph Yobo was kidnapped in Port Harcourt. Nornu Yobo was released after 10 days but it was never made clear whether a ransom was paid.
Chelsea offered Mikel their support in a statement, which read: “Everyone at Chelsea Football Club was very concerned to hear that John Mikel Obi’s father has been reported as missing and possibly abducted.
“We will give Mikel and his family our full support at this most difficult time.”
Nigeria is almost evenly split between Muslims in the north and the predominantly Christian south. Plateau state, in Nigeria’s fertile central belt, has seen thousands die in recent years in religious and ethnic violence.
Mikel’s family, from the Igbo tribe, are a minority in the area.