Mattingly traveled to Miami to meet with Marlins officials on Monday, according to multiple reports. The Miami Herald reported that a contract for Mattingly, 54, could be agreed to within days.
The Marlins began their search earlier this month, after it was determined Dan Jennings would not return in the role next season. Jennings had made the unusual move from GM to manager when the Marlins fired Mike Redmond in May after a 16-22 start.
The change failed to spark a turnaround, and the injury-riddled Marlins finished 71-91 for their sixth consecutive losing season.
The Dodgers, meanwhile, were careful not to portray Thursday's separation from Mattingly as a firing, and Mattingly declined to call it a resignation.
"When we started on Friday, we expected him to be our manager in 2016,'' president of baseball operations Andrew Friedman said.
Mattingly had one year remaining on his contract with the Dodgers. The sides discussed a possible contract extension, but the Dodgers never officially offered Mattingly one, according to Friedman. By Wednesday, both sides had agreed it was time for Mattingly to move on.
Mattingly said he would like to manage again, but he wasn't sure whether the opportunity would arise in 2016. Asked whether he could envision sitting out a year before reentering the fray, he replied, "Sure."
After the week of discussions with the Dodgers, sources indicated to ESPN's Ramona Shelburne that Mattingly simply felt he would be more comfortable working for a front office and ownership group that had hired him, instead of trying to adapt to someone else's vision. With the Dodgers, Mattingly had worked under two ownership groups and two general managers.
Information from ESPN's Mark Saxon and The Associated Press was used in this report.