Eaton played college baseball for Miami University before the Diamondbacks selected him in the 19th round of the 2010 MLB draft.

He is the fourth player to reach the major leagues from Kenton Ridge, preceded by Dave Burba, Rick White and Dustin Hermanson.

[2] He played for the Miami RedHawks baseball team in the Mid-American Conference (MAC) in NCAA Division I.

[15] Eaton was expected to play for the Diamondbacks for the 2013 season, but suffered an injury to his right elbow during spring training.

During spring training in 2015, Eaton and the White Sox agreed to a five-year contract extension worth $23.5 million, with options for two additional years.

[20] On December 7, 2016, the White Sox traded Eaton to the Washington Nationals for Lucas Giolito, Reynaldo López, and Dane Dunning.

[21] On Opening Day, Eaton went 1-for-2, was walked twice, stole a base, scored a run, and hit a double against the Miami Marlins.

The next day, on April 29, Eaton was diagnosed with a left knee strain, placing him on the 10-day disabled list.

He got off to a hot start at the plate to begin the season, winning the first National League Player of the Week award of the year (and in his career) after going 8-for-13 with two home runs against the Cincinnati Reds in a three-game series.

[25] However, Eaton continued to move awkwardly on his surgically repaired left leg, and after exiting a game against the New York Mets early on April 5 following an aggressive sliding play at the plate to score a run,[26] he was ultimately placed on the disabled list with what was described as a bone bruise in his left ankle on April 11.

[28] Following the chondral flap operation and a brief rehab assignment with the Class-AA Harrisburg Senators and High-A Potomac Nationals, Eaton was activated from the disabled list for a start in right field against the San Francisco Giants at Nationals Park on June 9.

[30] The Nationals finished the year 93–69, clinching a wild card spot and winning the World Series over the Astros.