Mariano Duncan Nalasco
- Bats Right, Throws Right
- Height 6' 0", Weight 185 lb.
- Debut April 9, 1985
- Final Game September 17, 1997
- Born March 13, 1963 in San Pedro de Macoris, San Pedro de Macoris, D.R.
Middle infielder Mariano Duncan played a dozen years in the majors and was a coach after his playing days.
Originally signed by the Los Angeles Dodgers and scout Rafael Avila in January 1982, Duncan made his pro debut that summer as a 19-year-old with the Lethbridge Dodgers, hitting .236 in 30 games. The following year, 1983, he hit .266 for the Vero Beach Dodgers and led the Florida State League with 15 triples and 56 stolen bases. After hitting .253 with 11 triples and 41 steals for the San Antonio Dodgers in 1984, he was Opening Day starter at second base for Los Angeles in 1985. He soon became the team's regular shortstop, hitting .244 with 38 stolen bases on the year, and finished third in Rookie of the Year voting. He hit .222 in the NLCS that year as the Dodgers fell to the St. Louis Cardinals.
Duncan's average dipped to .229 in 1986 but he stole 48 bases, fourth best in the National League. However, after he hit just .215 in 1987, he did not appear in the majors in 1988, missing the Dodgers' run to a World Series title. Back with Los Angeles in 1989, he hit .250 in 49 games before being traded to the Cincinnati Reds in July as part of a four-player deal. In 1990, he was the Reds regular second baseman, hitting .306 and leading the NL with 11 triples as Cincinnati won the NL West crown. He hit .300 in an NLCS win over the Pittsburgh Pirates, and then went 2-for-14 in the World Series as the Reds captured a World Championship.
After the 1991 season, Duncan became a free agent and moved on to the Philadelphia Phillies. After playing for the Phils in the 1993 World Series, he was the starting second baseman for the NL in the 1994 All-Star Game. After returning to the Reds late in the 1995 campaign, he moved on to the New York Yankees in 1996 and hit .340 in 109 games. He hit .313 in the ALDS but went just 1-for-19 in the World Series; the Yankees defeated the Atlanta Braves in six games nonetheless. Midway through the 1997 season, he was traded to the Toronto Blue Jays for Angel Ramirez. He spent 1998 in Japan, hitting .232 for the Yomiuri Giants.
A natural right-handed hitter, the Dodgers tried to turn him into a switch-hitter to take advantage of his speed, but he was never much of a hitter lefthanded. He went back to hitting full-time from his natural side when he was sent back to the minors in 1988.
Following his playing days, Duncan was a coach for the GCL Dodgers in 2003, Jacksonville Suns in 2004, and Las Vegas 51s in 2005. He was named Los Angeles Dodgers first base coach in 2006, a role he filled for five seasons, until 2010. He moved to the Tennessee Smokies as coach in 2011 and 2012 and Daytona Cubs in 2013 and 2014. He was then coach for the Myrtle Beach Pelicans in 2015-2016 and co-hitting coach of the Iowa Cubs in 2017. In 2018, he moved to the Detroit Tigers organization as hitting coach for the West Michigan Whitecaps. Moving again, the New York Mets' chain, he was a coach for the Kingsport Mets in 2019 and bench coach for the Brooklyn Cyclones in 2021.
- NL All-Star (1994)
- NL Triples Leader (1990)
- Won two World Series with the Cincinnati Reds (1990) and the New York Yankees (1996)