Barring any last minute changes,Davey Johnson will manage one last season and then become a special adviser to General Manager Mike Rizzo in 2014. (Alex Brandon/Associated Press)

As the Washington Nationals and Manager Davey Johnson near a final resolution for Johnson to manage next year, the sides agree that the 2013 season will be Johnson’s last, according to a person familiar with the talks.

The Nationals and Johnson remain on the verge of completing a deal that officially would make him Washington’s manager again for 2013. Barring a change of plans during the next year, Johnson will manage one last season and then become a special adviser to General Manager Mike Rizzo in 2014.

Johnson, who will turn 70 in January, said after the conclusion of this past season that he would have considered “pulling a La Russa” — retiring from managing — had the Nationals won the World Series, as Tony La Russa did after leading the St. Louis Cardinals to the 2011 title. Instead, Johnson cited “unfinished business” and a desire to return for another season as the oldest manager in baseball.

Johnson took over as the Nationals’ manager in June 2011, following Jim Riggleman’s abrupt resignation. Johnson signed a three-year contract that made him a consultant for the 2013 and 2014 seasons with the agreement that the deal could be tweaked to make Johnson the manager. While the sides are still polishing off those tweaks, Rizzo said he expects the deal to be made official shortly.

Rizzo has said he wants Johnson’s successor to come from within the organization. Bench coach Randy Knorr appears to be the leading candidate, with first base coach Trent Jewett, Class AAA Syracuse Manager Tony Beasley and Class AA Harrisburg Manager Matt LeCroy also possibilities.

Note: First baseman Adam LaRoche declined his one-year, $13.3 million qualifying offer prior to Friday’s 5 p.m. deadline, according to the MLB Players Association. The Nationals will receive a compensatory draft pick if LaRoche signs elsewhere this winter. The Nationals are still permitted to sign LaRoche, who has said he prefers to remain in Washington. Rizzo said Thursday that he still wants to keep LaRoche with the Nationals.