Nieto, a fifth-round selection in the 2008 First-Year Player Draft out of baseball-rich American Heritage High School in Plantation, Fla., has played sparingly as a professional.
A catcher by trade, the switch-hitter spent the 2008 and '09 campaigns playing for Washington's affiliate in the Gulf Coast League, and he batted .195 in 60 games for Class A Hagerstown last season.
A native of Havana, Cuba, Nieto will serve his suspension from the outset of the 2011 regular season. The Nationals spent $376,000 to convince Nieto to forego college and sign after the '08 Draft, giving him more than twice the expected price for his draft slot.
Nieto, just 20 years old, will likely begin his season with a repeat engagement at Hagerstown after serving his suspension.
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.