The hiring of a new manager is usually a signal of a change of direction for a baseball franchise. It is the dawn of a new era. In many cases, the new manager is a sharp contrast to the prior manager, sometimes the exact opposite. Teams lament in the glory of how the symbol of their new manager is the start of a new run of success that is coming to said franchise. Of course, it does not always bear such fruit. Even so, conventional wisdom would say the manager needs more than just one season before it is decided he is not the answer.
Among the six managers hired prior to the 2018 season, two managers have led their teams to the two of the best records in all of baseball, and another has led his team to the lead of his respective decision. It is safe to say that Alex Cora, Aaron Boone, and Gabe Kapler will all be back for their second season. Ron Gardenhire took over the Detroit Tigers after they have started their rebuild. Teams do not get rebuilt in a season.
As for Davey Martinez and the Washington Nationals, expectations were much higher coming into a season in which many considered this the last chance of making a quality postseason run. With free agents looming such as Bryce Harper, Daniel Murphy, and Gio Gonzalez, it is expected the Nationals will look very different in 2019. Is Martinez the reason the Nats have under performed? Blaming the Nationals manager seems to be the way General Manager Mike Rizzo seems to operate. But, even the most narrow minded baseball brain can see through that clouded logic. It would be wise for Rizzo to bring Martinez back for 2019. Only in the spirit of George Steinbrenner running the New York Yankees during the 1980's would letting Martinez go after this season even have something to compare to.
The only way New York Mets manager Mickey Callaway loses his job this season is if the Mets decide to bring in a new General Manager from outside the organization. In this case, it would be up to the new GM to decide who he (or she) felt was best suited to manage the team going forward.
The last time a MLB manager was let go after just one full season was in 2014. It was a bizarre situation- one that the incumbent manager was not to be blamed for. Rick Renteria was let go after just one season for only one reason- the fact that the Chicago Cubs could hire Joe Maddon, himself let out of his contract as the Tampa Bay Rays. Bobby Valentine managed the Boston Red Sox for one tumultuous season in 2012, one in which everything that could possibly go wrong, did. In fact, Valentine's example is a rare one in which a team quickly identified it made a mistake.
Dick Howser managed the Yankees to 103 wins in his only season as skipper in 1980. He was let go because the Yankees were bounced out of the playoffs three consecutive games in the American League Championship Series. The San Diego Padres hired Jerry Coleman to manage the team for the 1980 season. After Coleman decided he would rather go back to the broadcast booth, the team hired Frank Howard to manage the team in 1981. Howard was not brought back for the 1982 season. Yogi Berra managed the Yankees to an American League Pennant in 1964. He was fired after the season, his only as the Yankees manager (until 1984 and the first 16 games of the 1985 season). Chuck Tanner managed the 1976 Oakland Athletics to 87 wins and was let go after his first season. Paul Richards took over the Chicago White Sox during the bicentennial after being out of the game for 15 years. He only lasted the one season.
Billy Martin led the 1969 Minnesota Twins to the first ever American League West division title with 97 wins. He was fired after the season, his first as a manager. One of his many stops in New York was the entire 1983 season, after which he was let go in favor of Berra. Of course, it was Martin who replaced Berra after 16 games in 1985.
While many examples exist in the history of baseball where managers have lasted just one full season, most of us can agree that giving up after one season is a little too soon. Of course, Valentine and Richards are exceptions to the rule and prove that a manager can either overstay his welcome or become more of a distraction and lead to a destruction of a franchise than was intended with the hire.