The Colorado Rockies selected Nelson in the first round, with the ninth overall selection, of the 2004 amateur entry draft,[2] and received the third largest signing bonus in Rockies history.[3] In July 2007, while playing for the Modesto Nuts, Nelson was named Rockies Farm Player of the Month.[4]
On September 9, 2010, Nelson stole home plate against Cincinnati Reds pitcher Nick Masset, scoring what would be the deciding run in the Rockies' victory, their seventh straight. It was Nelson's first career stolen base, and the first time he had stolen home plate at any level.[6]
Though he struggled at the MLB level during the 2011 season, Nelson was announced as the third base starter along with Jordan Pacheco during Spring Training in 2012. He was designated for assignment on April 28, 2013.[7]
New York Yankees
On May 1, Nelson was traded to the New York Yankees.[8] On May 15, he was designated for assignment to make room on the roster for David Adams.[9]
Los Angeles Angels of Anaheim
On May 18, 2013, Nelson was claimed off waivers by the Los Angeles Angels of Anaheim.[10] He was designated for assignment on June 10, 2013,[11] and accepted an assignment to the Triple-A Salt Lake Bees on June 13.[12] Following the trade of Alberto Callaspo on July 31, Nelson's contract was selected from Salt Lake.[13] On August 15, he hit his first career grand slam against Yankees reliever Boone Logan.[14] After the season, Nelson was non-tendered by the Angels, making him a free agent.[15]
Cincinnati Reds
On January 28, 2014, Nelson signed a minor league deal with the Cincinnati Reds.[16] On June 16, 2014, Nelson was released by the Reds.[17]
San Diego Padres
On June 19, 2014, Nelson signed a minor league deal with the San Diego Padres.[18] On July 18, 2014, Nelson was called up from Triple-A El Paso and made his Padres debut against the New York Mets, going 2–4 with 2 RBI.[19][20] He was designated for assignment on September 2, 2014. Nelson elected free agency in October 2014.[21]
Philadelphia Phillies
Nelson signed a minor league deal with the Philadelphia Phillies on November 25, 2014.
Milwaukee Brewers
Nelson signed a minor league deal with the Milwaukee Brewers on May 9, 2015. And he was released on June 17, 2015.
Washington Nationals
Nelson signed a minor league deal with the Washington Nationals on June 21, 2015. He was released by the Washington Nationals on July 25, 2015.
Colorado Rockies (second stint)
On February 15, 2016, Nelson signed a minor league contract to return to the Colorado Rockies organization. In 69 games for the Triple–A Albuquerque Isotopes, he batted .232/.273/.310 with three home runs and 33 RBI. Nelson elected free agency following the season on November 7.[22]