The Marlins are expected to reintroduce McKeon as manager at the 3 p.m. ET news conference at Sun Life Stadium, eight years after winning a championship and six years removed from his last season in a dugout.
According to a source, McKeon will be named Florida's interim manager a day after Edwin Rodriguez unexpectedly resigned on Father's Day. He will close out the 2011 season, and the team is expected to make a full-scale managerial search before it moves into its new ballpark in '12.
At age 80, McKeon will be the second-oldest manager in Major League history. Only the legendary Connie Mack was older, managing the Philadelphia Athletics -- a team he owned -- past his 87th birthday.
This will be McKeon's second stint managing the club. But he's remained with the organization since 2005 as a special assistant to owner Jeffrey Loria. The savvy, seasoned, career baseball man has remained active with the franchise, scouting its Minor League system as well as representing the team at the First-Year Player Draft.
McKeon first joined Florida on May 11, 2003, when the franchise decided a different voice was needed after it fell to 16-22 under Jeff Torborg.
Making a bold move, the Marlins hired McKeon, who was 72 years old at the time.
McKeon entered a youthful clubhouse as the third-oldest manager in MLB history -- behind Mack and Casey Stengel (75). Results didn't come immediately, as the team fell 10 games under .500 on May 22.
But from May 23 and forward, the Marlins went on a roll and they pulled off one of the greatest upsets in modern baseball history.
Under a cigar-chomping, old-school manager, a young Florida squad secured the National League Wild Card berth and went on to win the World Series.
The Marlins celebrated the second World Series title in franchise history by defeating the heavily favored Yankees in six games. Going with gut instincts and grit, McKeon sent 23-year-old Josh Beckett to the mound on three days' rest.
Beckett tossed a shutout in a classic close-out game at Yankee Stadium.
The Marlins once again are making a midseason managerial move. On Father's Day morning, Rodriguez turned in his resignation after his team dropped nine straight and 17 out of 18 in June.
Bench coach Brandon Hyde managed the club on Sunday in a 2-1 loss to the Rays at Tropicana Field.
McKeon managed the Marlins from 2003-05, where he guided the franchise to three straight winning seasons and a 241-207 record. He has the distinction of winning 1,000 games as an MLB and Minor League manager. His MLB mark is 1,011-940, and in 17 Minor League years, he was 1,146-1,123.
Twice, he was named the National League Manager of the Year, in 2003 with Florida and 1999 with the Reds.
This is the second straight year the Marlins have changed managers in midseason. In 2010, Rodriguez replaced Fredi Gonzalez on June 23.
At the time Rodriguez was named, the Marlins were two games under .500, and they finished 80-82. The team was 46-46 under Rodriguez last year, and 32-39 this season.
McKeon's hiring in 2003 came on Mother's Day, and at a time when the season appeared lost.
Turning the clock back eight years, the Marlins certainly weren't well placed in the standings at this time of year. In fact, on June 19, 2003, they posted a 35-39 record, and they were 13 games behind the Braves, locked in fourth place.
Rodriguez stepped down with the team at 32-39, 12 1/2 games back of the Phillies in the NL East.