Early career

Leiter was raised in a baseball-oriented family; all five of his brothers played the game.^[1] A native of Berkeley Township, New Jersey,^[2] Leiter attended Central Regional High School, in the township's Bayville section.^[3] During one stretch in high school, he pitched consecutive no-hitters followed by a 32-strikeout game in 13 innings on April 19, 1984 (a game which ended in a tie when it was called for rain).^[1][4] Leiter was selected for the Wilson First Team All-American team. In 2016, the NJSIAA named Leiter to the NJ High School Hall of Fame.

New York Yankees

Leiter was drafted by New York Yankees in 1984 MLB draft as a second round pick. Both he and his brother Mark became Yankees prospects.

Leiter made his MLB debut as the starting pitcher for the Yankees on September 15, 1987, earning the win in a Yankees 4–3 victory over the Milwaukee Brewers at Yankee Stadium. Leiter has mentioned on a YES Network broadcast that early in his career with the Yankees, manager Billy Martin walked up to him and asked him why he was lifting weights. Leiter responded, "To strengthen my arm." Billy was quoted as saying, "If you want to strengthen your arm, do some long toss." The young Leiter grew nervous easily; teammate Tommy John observed "If they had named him to start on opening day [in 1989], he wouldn't have slept for a week. That's how high-strung he was. He was a rookie bouncing off the walls."^[5] In one of his final starts as a young player for the Yankees, manager Dallas Green left Leiter in to throw 162 pitches on a cold damp day in 1989.

Toronto Blue Jays

The Yankees traded him to the Toronto Blue Jays for outfielder Jesse Barfield on April 30, 1989.^[6] After being dealt to Toronto, the left-hander had arthroscopic surgery. He pitched in fewer than 20 innings for the Blue Jays from 1989 to 1992, because of the surgery, a pinched nerve in his elbow, tendinitis, and another arthroscopic surgery on his left shoulder. His statistics during this period were a 5.17 ERA, 15+2⁄3 IP, 14 H, 10 K, 11 BB, 1 HR, 1 GS, 0–0. He was, however, able to overcome a blisters problem with an exotic liniment (that he used throughout his career), and was still seen as a very promising prospect.

Leiter finally got over his injury troubles in 1993, making 32 appearances (12 starts) for the Blue Jays. That year he appeared in 5 postseason games and even picked up a win in relief in Game One, and hit a double in Game Three of the 1993 World Series, as the Blue Jays went on to win their second consecutive World Championship. Leiter pitched effectively for the Blue Jays for the next two seasons before departing via free agency in 1996.

Florida Marlins

Following the 1995 season, Leiter left Toronto and signed with the Florida Marlins as a free agent. In his first season as a Marlin, Leiter made his first All-Star team, going 16–12 with a 2.93 ERA and 200 strikeouts.

On May 11, 1996, he pitched a no-hitter against the Colorado Rockies, the first no-hitter in Marlins franchise history.^[7][8] This was also the first no-hitter that included a three-pitch inning.^[9] Leiter was also selected to his first All Star game. The game was played at Veterans Stadium in Philadelphia where he recorded the last out of a National League 6–0 win over the American League. The win was the last NL win for 13 years until 2010 when the National League won the All Star Classic in Anaheim.

In 1997, Leiter won another World Series as the Marlins beat the Cleveland Indians. Leiter started Game 7 for the Marlins, pitching 6 innings and giving up two earned runs while being credited with a no decision. The Marlins would go on to win the game 3–2 in 11 innings to capture the championship.

New York Mets

Leiter with the Mets in 2004

In the following off-season, Leiter was traded to the New York Mets in part of the Marlins' fire sale where owner Wayne Huizenga traded away almost all of the team's higher priced players.

In Leiter's first season as a Met, he reached a career high in wins going 17–6 and a career low in ERA finishing with a 2.47 ERA. In 1999, when the Mets were tied with the Cincinnati Reds for the National League Wild Card spot after 162 games, Leiter was the Mets starting pitcher in the "winner take all" one game playoff at Cinergy Field in Cincinnati. Leiter pitched a 2-hit shutout to earn the win in the Mets 5–0 victory. The win put the Mets in the playoffs for the first time in 11 seasons. The Mets would go on to lose the 1999 National League Championship Series to the Atlanta Braves 4 games to 2.

In 2000, Leiter made the All-Star team once again going 16–8 with a 3.20 ERA and 200 strikeouts. The Mets made the playoffs again in 2000 and this time reached the World Series. Leiter started Game 1 of the 2000 World Series at Yankee Stadium and Game 5 at Shea Stadium. Although he managed to achieve a 2.87 ERA and 16 strikeouts in 15+2⁄3 innings, the Mets lost both games he started and eventually lost the World Series 4 games to 1. He was booed by Yankee fans when presented that year's Roberto Clemente Award prior to Game 2 of the World Series. Leiter was the second New York Met to be honored with the award. During the 2000 season, he pitched in the All Star game, and gave up a single to Derek Jeter.^[10]

On April 30, 2002, Leiter became the first Major League pitcher to defeat all 30 teams, after beating the Arizona Diamondbacks 10–1.^[11][12] Leiter would pitch for the Mets until the end of the 2004 season. In his seven seasons in a Met uniform, all wearing number 22, he went 95–67 with a 3.42 ERA. At the time he left the Mets, he ranked highly on several Mets all-time lists including wins (6th), strikeouts (7th with 1106), innings pitched (7th with 1360.0), and games started (6th with 213). He was the Mets Opening Day starting pitcher in 1999, 2001, and 2002.

In ten straight seasons, from 1995 to 2004, Leiter had at least 10 wins and at least a .500 record.

Second stint with Marlins

Following the 2004 season, the Mets declined Leiter's US$10 million option for 2005, making him a free agent. His former team, the Marlins, signed Leiter to a one-year, $8 million contract on December 8, 2004.

Leiter struggled during his return to the Marlins. He walked more batters than usual (60 in 80 innings, in addition to 88 hits). In 17 appearances (16 starts), he had a 3–7 record and a 6.64 ERA, and he took much criticism for the Marlins' first-half struggles in 2005 (they were 7 games behind the surprising Washington Nationals at the All-Star break). He was demoted to the bullpen in late June, but he returned to the rotation after an injury to Josh Beckett. On July 10, when the Marlins played their last game before the three-day All-Star break, he gave up six runs in three-plus innings.

On July 14, 2005, the Florida Marlins designated Leiter for assignment.

Second stint with Yankees

On July 15, 2005, Leiter was acquired by the New York Yankees, who had four starting pitchers on the disabled list, for a player to be named later. His first start as a Yankee since April 26, 1989, came on July 17, 2005, against the division-leading Boston Red Sox. Leiter won the game, pitching 6+1⁄3 innings, allowing one run and three hits, and striking out eight. After several starts with mixed success, he informed Joe Torre that he would be willing to pitch out of the bullpen, where he would stay for the latter part of the season, yielding his starting slot to Aaron Small.

Leiter worked out of the bullpen in the 2005 American League Division Series pitching in four of the five games between the Yankees and Los Angeles Angels of Anaheim. The Angels won the series 3 games to 2. In his final official appearance in a Major League uniform, Leiter earned a win, pitching 2⁄3 scoreless innings in Game 4 at Yankee Stadium. The Yankees won the game 3–2.

Leiter signed a minor league contract with the Yankees in 2006; however, he stated he would likely retire. The primary reason he spent part of spring training with the Yankees was to keep in shape for the World Baseball Classic. After the United States team was eliminated from the World Baseball Classic, he officially retired in an interview on YES, after a Yankees spring training victory versus the Indians where Leiter pitched 1⁄3 of an inning.^[13]