He played in Major League Baseball (MLB) for the Arizona Diamondbacks, Philadelphia Phillies, Milwaukee Brewers, Pittsburgh Pirates, New York Mets, and Houston Astros.

Figueroa attended Brandeis University from 1992 to 1995, where he pitched for three years and earned a bachelor's degree in American Studies.

The Mets traded Figueroa with outfielder Bernard Gilkey to the Arizona Diamondbacks in 1998 for Jorge Fábregas, Willie Blair and cash considerations.

On July 26, 2000, Figueroa was traded with Vicente Padilla, Travis Lee, and Omar Daal to the Philadelphia Phillies for Curt Schilling.

Figueroa spent the rest of the 2000 season pitching for the Scranton/Wilkes-Barre Red Barons of the International League (AAA), compiling a record of 4–3 and an ERA of 3.78.

After a brief stint with the Pirates in 2004, Figueroa spent 2005 rehabilitating a torn rotator cuff that he had played with during the previous season.

He signed a minor-league contract with the Washington Nationals early in 2006 and spent the season pitching for the Triple-A New Orleans Zephyrs, where he posted a 4.38 ERA in 76 innings of work.

Figueroa went to Taiwan in September 2007 as a late season addition to the Uni-President Lions of the Chinese Professional Baseball League (CPBL).

Nelson was called up on April 19, 2009, to start against the Brewers in place of injured Mike Pelfrey, and was designated for assignment following the game.

On October 4, 2009, the last day of the 2009 MLB regular season, Figueroa tossed a four-hitter and struck out seven batters for the first complete game and shutout (4–0) of his major league baseball career.

On August 23, 2011, Figueroa signed a minor league contract with the Pittsburgh Pirates and was assigned to the Triple-A Indianapolis Indians.

On March 3, 2022, Figueroa was announced as the new pitching coach for the Staten Island FerryHawks of the Atlantic League of Professional Baseball.

[12] On January 31, 2023, Figueroa was announced by the Long Island Ducks of the Atlantic League of Professional Baseball as their new pitching coach.

Following the conclusion of the tournament, which was won by Dominican Republic upon beating Puerto Rico in the final, Figueroa was named to the All-WBC team.

[15][16] During the second game played against the United States, Figueroa was the starting pitcher at age 38 and allowed just two hits in six scoreless innings.