Showalter has earned a reputation for building baseball teams into postseason contenders in short periods of time.

[1] He helped the Yankees rise from the bottom half of the AL East to first place before a players' strike prematurely ended the 1994 campaign.

Before becoming a teacher, his father had been a Little All-American fullback in 1940 at Milligan College, and had considered a career in the National Football League with the Pittsburgh Steelers, but chose to become a high school coach instead.

[7] Showalter was hired as manager of the Single-A minor-league Oneonta Yankees of the New York–Penn League in 1985, leading them to 114 victories in two seasons.

[citation needed] In 1990, Showalter was promoted to the coaching staff of the New York Yankees, and eventually succeeded Stump Merrill as the team's manager for the 1992 season.

However, Showalter could not watch the Yankees win the World Series, saying, "I feel badly for the fans" in New York for what they lost during the 1994 strike.

Named the Arizona Diamondbacks, Showalter was interested in taking a more active role in developing the eventual roster, complete with a $7 million contract for seven years.

He had a handshake deal with the team, but Yankees owner George Steinbrenner made one last ditch effort to his home in Florida about wanting him back (Joe Torre had been tapped to manage for the moment).

[21] In the Diamondbacks' first season (1998), Showalter managed the team to a 65–97 record, but following numerous off-season player acquisitions, which included Randy Johnson, Armando Reynoso, Todd Stottlemyre, Luis Gonzalez, Tony Womack, and Steve Finley, Showalter managed the 1999 team to a 100–62 record and the National League West title, making them the fastest expansion team in MLB history to win a division title.

The Rangers failed to make the playoffs, finishing third in the AL West, though Showalter was again named Manager of the Year.

[18] Showalter was hired as a senior advisor to baseball operations for the Cleveland Indians on December 1, 2006,[25] and then returned to ESPN as an analyst, before being appointed to succeed Juan Samuel as manager of the Baltimore Orioles on July 29, 2010.

[citation needed] Under Showalter, the Orioles reached the postseason for the first time since 1997, defeating the Texas Rangers in the Wild Card game on October 5, 2012.

[34] After finishing out of playoff contention in the 2013 season, Showalter led the 2014 Orioles to the AL East title—the franchise's first in 17 years.

They made the postseason for the third time in five years, but lost 5–2 in 11 innings to the Toronto Blue Jays during the AL Wild Card game.

[citation needed] On October 3, 2018, days after the Orioles finished with a franchise-worst 115 losses, Showalter's and General Manager Dan Duquette's contracts ran out and the team announced that they would not be brought back.

Amid a disappointing start to the 2023 season, in the words of The Athletic's Tim Britton, Showalter's performance came "under justified fire" from fans.

[41] Showalter then announced on the final day of the season that he was fired as Mets manager by newly appointed President of Baseball Operations David Stearns.