Despite being a 36th round draft pick, Downs reached the major leagues in 2009, starting at second base temporarily for the Giants during the season.

Downs graduated from Bibb County High School in Centreville, Alabama, following which he played a year as a pitcher/infielder for Shelton State Community College in 2003.

In 73 games (tied with Garrett Baker and Helder Velazquez for second in the league behind Darin Holcomb), he hit eight home runs and had 48 RBI.

[1][13][14] Downs started five games in a row at second on this stint; after recording two hits in 17 at-bats, he was returned to Fresno where he finished the season.

[18] At the beginning of May, he became the Giants' everyday second baseman when Uribe was moved to shortstop to replace the injured Édgar Rentería.

[19][20][21] Downs batted .264 with five RBI in 15 games as the Giants' second baseman, but on May 19, he returned to a utility role as Freddy Sanchez was activated from the disabled list.

[19] Downs was designated for assignment by the San Francisco Giants on August 23 to make room for Cody Ross.

[1] Downs was claimed off waivers by the Houston Astros on August 25 and sent to the Triple-A Round Rock Express of the Pacific Coast League.

[27] He had a game-winning double against Nick Masset on April 7, giving the Astros their first victory of the year as they defeated the Cincinnati Reds 3–2.

[28] On June 22, he hit a game-winning, pinch-hit, two-run home run against Neftalí Feliz as the Astros defeated the Texas Rangers 5–3.

[30] Three days later, he had a game-winning, pinch-hit, three-run double against Matt Reynolds as the Astros beat the Colorado Rockies 9–6.

[32] His home run against Clayton Richard accounted for all of the scoring on June 27 as the Astros beat the San Diego Padres 1–0.

[34] He was optioned to the Oklahoma City RedHawks of the Pacific Coast League on August 9 to make room for the newly acquired Tyler Greene on the roster; however, he was recalled on September 1.

[37] On January 31, 2013, the Miami Marlins signed Downs to a minor league contract with an invitation to spring training.