The right-handed hitting Navarro was signed by Boston as a non-drafted free agent in 2005 and made his big league debut with Red Sox on August 20, 2010. In his Major League career, he has made 20 appearances at third base, 19 at shortstop and three at second base.
Navarro entered the 2011 season ranked by Baseball America as Boston's 12th-best prospect. He was a mid-season South Atlantic League All-Star while playing with Greenville in 2008 and a New York-Penn League mid-season All-Star while playing with Lowell in 2007.
In six minor league seasons, Navarro has produced a .279 batting average, a .348 OBP, 100 doubles, 20 triples, 43 home runs and 264 RBI in 470 games.
The Pirates will announce a corresponding roster move on Thursday to make room for Navarro on the 40-man roster.