On June 23, 2011, Jim Riggleman resigned from his post as the Washington Nationals' manager, convinced he wasn't in the team's longterm plans. The Nationals didn't look far for his eventual replacement, quickly hiring front office consultant Davey Johnson, who returned to the dugout after a hiatus of nearly 11 years. Johnson will manage the Nationals for the rest of the season and has an option to return for 2012, according to MASN. At whatever point he is done with managing, he will stay in the Nationals front office to help hire his successor.
How good of a manager did the Nationals pick? The career .563 winning percentage he carried from stints with the Mets, Reds, Orioles and Dodgers, which ranks eighth all time among managers who skippered at least 1,000 games after 1900, suggests he either had something on the ball or stumbled into some awfully talented rosters.
As unlikely as the latter sounds, one is hard-pressed to refute it without resorting to anecdote instead of data; managerial skills are not readily defined statistically. The majority of a manager's impact on a team is arguably behind the scenes.
Even when a manager does push a button for a bunt or call for a particular reliever, just because it works out doesn't mean he was right, and if a given move doesn't pay off, it doesn't mean he was wrong. The best the manager (and fans) can hope for is to have a good rationale for his decisions. The actual execution is up to the player.
Where the manager has the most direct impact is in deciding who to play. Baseball is distinct among the major sports in that a team's probability of winning changes daily, simply based on the availability of his players.