The Union selected Colorado Rapids forward Conor Casey in the second stage of the MLS reentry draft on Friday.
Casey, 31, suffered an Achilles tendon tear in 2011 but played in 18 games last season for Colorado, scoring two goals and adding three assists. The 2010 MLS Cup MVP, he has 50 goals in seven MLS seasons and has made 20 appearances with the U.S. national team.
"Conor makes us a better team," team manager John Hackworth said in a statement. "He has proven that he can be one of the best forwards in this league and for the national team. Our staff believes that Conor still has many goals left in him."
Under the rules of the reentry draft, the Union are able to offer Casey a lower salary than the $400,000 he earned last season. If the two sides cannot reach an agreement, the Union retain the right of first refusal on Casey if he plays in MLS.