[2] After Nieto graduated, the Washington Nationals selected him in the fifth round of the 2008 Major League Baseball (MLB) Draft.

[5] In 2011, he was suspended for 50 games for violating the league's performance-enhancing drug policy after testing positive for an anabolic steroid.

He split the year between the Low-A Auburn Doubledays, Hagerstown, and the High-A Potomac Nationals, accumulating a .278/.360/.450 batting line with career-highs in home runs (7) and RBI (34).

[3] Because Nieto was a Rule 5 pick, he had to be on the Chicago White Sox roster for the entire season, so for 2014, he was the backup to Tyler Flowers, batting .236/.296/.340 in 48 games.

[12] He was assigned to the Triple-A Louisville Bats, and also spent time with the Double-A Pensacola Blue Wahoos, but was released by the Reds organization on August 27 after hitting a cumulative .230/.282/.323 with 3 home runs and 21 RBI.

[14] He split the remainder of the season between the Double–A Jacksonville Jumbo Shrimp and the High–A Jupiter Hammerheads, posting a cumulative .188/.233/.288 slash line with two home runs and seven RBI.

[16] Nieto did not play a game for the team because of the cancellation of the 2020 ALPB season due to the COVID-19 pandemic and became a free agent after the year.