UPDATE (8:57 PM EST): Apparently this entire situation is related to the pitcher's immigration status. According to Steven Wine of the Associated Press, Nunez has been living in the U.S. under an assumed name and needed to return to the Dominican Republic in order to sort out the situation. Wine adds that the Marlins have been aware of the issue for months, and one of the report's sources says that Nunez's real name is actually Juan Carlos Oviedo; he's also 29 years old, rather than 28.
ORIGINAL REPORT (5:02 PM EST): The Marlins placed closer Leo Nunez on the restricted list earlier today, initially for undisclosed reasons. We've seen learned that Nunez isn't being disciplined for behavior, as Juan C. Rodriguez of the South Florida Sun-Sentinel is reporting that Nunez was placed on the list while he handles personal matters in his native Dominican Republic.
The move, first reported by Clark Spencer of the Miami Herald, temporarily removes Nunez from Florida's 25-man and 40-man rosters. There's a possibility that Nunez loses some pay for this stint, as teams don't always pay players when they're put on the restricted list, particularly when the MLBPA doesn't object.
It seems unlikely that Nunez, 28, will lose any of his $3.65 million salary over the situation, and most indications are that the club expects to retain its closer for next season. He's posted a 4.06 ERA with similar peripherals and 36 saves over the course of 68 appearances with the Marlins this season.