Calero is a graduated from
University Gardens High School in
Puerto Rico and attended
Miami-Dade College Kendall Campus. He was drafted by the
Detroit Tigers in the 41st round (1142nd overall) of the
1994 Major League Baseball draft, but Calero did not sign with the Tigers. Instead he attended
St. Thomas University (Florida) and was drafted again in the
1996 Major League Baseball draft, when he was picked in the 27th round (799th overall) by the
Kansas City Royals.
Kansas City Royals Mainly a
starting pitcher in the Royals minor league organization, he spent 6 years at the Single-A and Double-A levels before finally reaching Triple-A
Omaha in . During his minor league career, Calero excelled for the Royals organization. In 1996, he finished fourth in the Single-A
Northwest League in
ERA. He was also named to the
Texas League All Star team in . Through , Calero had 31 wins in a
Wrangler uniform and worked as a reliever in after 105 starts. The Royals traded Calero to the
Philadelphia Phillies for shortstop
Brian Harris in 2002 but was returned to the Royals and granted free agency.
St. Louis Cardinals Calero was subsequently signed as a
free agent by the
St. Louis Cardinals. He made his Major League debut on April 2, 2003, for the Cards against the
Milwaukee Brewers, he worked two thirds of an inning, allowing two hits and one walk but no runs. He spent all of and most of in the majors. He played all but one game as a reliever. He was a member of the 2004 St. Louis Cardinals' team that went on to win the
National League title and played in the
2004 World Series.
Oakland Athletics After the 2004 season, Calero was traded from the Cardinals along with starting pitcher
Dan Haren and top-hitting prospect
Daric Barton to the
Oakland Athletics for
Mark Mulder.
Texas Rangers On July 4, 2008, After being designated for assignment and released by the Athletics, Calero signed with the
Texas Rangers. The Rangers signed Calero to a minor league contract and assigned him to Triple-A Oklahoma, where he spent the rest of the season.
Florida Marlins Calero signed a minor league contract with an invitation to spring training with the
Florida Marlins in January . He made the team out of spring training, and was added to the major league roster on April 4. He became a free agent following the season.
New York Mets/Los Angeles Dodgers On March 4, 2010, the
New York Mets signed Calero to a minor-league deal with an invitation to spring training. On May 16, he was released by the Mets and he signed with the
Los Angeles Dodgers on June 10 and was assigned to the AAA
Albuquerque Isotopes. He appeared in 15 games for the Isotopes before they also released him. ==Overseas career==