Florida Marlins closer Leo Nunez has been playing under an assumed name, and the issue prompted him to return Thursday to his native Dominican Republic, two people familiar with his immigration status said.
Both people said the Marlins have been aware of the issue for several months. They spoke to The Associated Press on condition of anonymity because Dominican and team officials haven't made any public comment on the case.
One of the people said Nunez's real name is Juan Carlos Oviedo and he's 29, a year older than listed in the team media guide. The Marlins placed Nunez on Major League Baseball's restricted list, and he isn't expected to pitch in the final week of the season.
His agent, Andy Mota, declined to comment. The Marlins traveled Thursday to Milwaukee for their final road series of the season.
Nunez has 36 saves and a 4.06 ERA in 68 games this year. His ERA was 2.59 in late May but is 6.00 since then.
The right-hander has an effective changeup and a fastball that reaches 97 mph, and in three seasons with Florida he has 92 saves. He pitched a scoreless ninth inning in Wednesday's victory over Atlanta.
Nunez, who is married, turned professional in 2000 when he signed with the Pittsburgh Pirates. He was traded to Kansas City in late 2004 and made his major league debut with the Royals the following season. The Marlins traded for him after the 2008 season.
According to his Marlins biography, he was born in Jamao al Norte, Dominican Republic, and lives in Bonao.
Nunez will be in his final year of arbitration after this season and was expected to make about $6 million in 2012. Even before the issue regarding his identity surfaced, it was unclear whether the Marlins would try to re-sign him.
The players' association had not immediately determined whether to challenge the Marlins' decision to place him on the restricted list, a person familiar with the union's deliberations said. The person spoke on condition of anonymity because the union had not made any public statements.