Hammonds was an outfielder and played for the Baltimore Orioles (1993–1998), Cincinnati Reds (1998–1999), Colorado Rockies (2000), Milwaukee Brewers (2001–2003), San Francisco Giants (2003–2004) and the Washington Nationals (2005) in Major League Baseball (MLB).

After he was traded to Cincinnati and then to Colorado, he emerged with the Rockies in 2000, and was selected to appear at the 2000 Major League Baseball All-Star Game.

He signed a three-year, $21.75 million contract with the Milwaukee Brewers that off-season, but continued to struggle with injuries.

He reported that he never considered going professional at that point, as his parents insisted he attend college, and that Hammonds' brother, who had signed with the Pittsburgh Pirates out of high school, suffered a career-ending injury while playing in minor league baseball.

[1][4] The Orioles, regarded as frugal, held a hard line with Hammonds in negotiations, refusing to give a signing bonus as large as $1 million.

[2] Hammonds did not play professionally in 1992[5] as he competed for the United States national baseball team in the 1992 Summer Olympics in Barcelona.

He faced a two-month road trip across sixteen states by bus, more travel combined with training than employed by any professional team.

[7] Hammonds received a promotion to the Orioles on June 25, becoming the first player chosen in the 1992 MLB draft to reach the majors,[1] where his debut was greeted with fanfare and high expectations.

[8] He batted .305 in 105 at-bats with the Orioles that season,[7] however he suffered a pinched nerve in May,[9] and a neck injury in August.

[14] When the Orioles needed to reduce their roster from 28 players to 25 in May 1995, Hammonds, who started the season batting 4-for-19, was optioned back to Bowie.

[13] After struggling with the Orioles early in the 1996 season, batting .237 in 56 games, he was demoted back to Rochester in June.

[19] With the threat of facing a salary arbitration hearing,[20] the Orioles approached him with the idea of working out an agreement on a multi-year contract extension.

In the May 19 contest versus the Colorado Rockies, Cincinnati won by a score of 24−12, tied for the fourth-highest run-scoring output in MLB history.

[28] After the season, the Rockies declined to offer Hammonds salary arbitration,[29] making him a free agent.

They initially assigned him to the Class-AAA Fresno Grizzlies of the Pacific Coast League, before promoting him on July 30.

[42] He batted .219 with one RBI in thirteen games for the Nationals, before returning to the disabled list with an injured hamstring on May 22.

[45] Hammonds' older brother, Reginald, played minor league baseball for the Pittsburgh Pirates' organization, reaching Class-AAA before suffering a career-ending injury.