D.C. United announced the signing of Emiliano Dudar, a 6-foot-4 Argentine center back who arrives from one of Switzerland’s top clubs, BSC Young Boys.

The former Swiss defender of the year will join returning regulars Dejan Jakovic, Brandon McDonald and Ethan White in the central defending corps. United didn’t have to pay a transfer fee. Terms of the contract weren’t disclosed.

Dudar, 30, suffered a serious head injury in the fall of 2010 and didn’t return until early last year. Consequently, United put him through a battery of tests in Washington this week before finalizing the deal.

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“He will provide our back line with a big, physical presence, excellent technical ability, and strong leadership qualities,” General Manager Dave Kasper said in a written statement.

Dudar didn’t play this past fall after falling out of favor with the coaching staff. United initially pursued a year-long loan — DCU would’ve paid a portion of his salary -- but Dudar and Young Boys decided to sever his contract with 18 months remaining.

United was intent on adding a fourth proven center back before the season started. Dudar’s acquisition also allows McDonald to play defensive midfield, if necessary. Perry Kitchen, the top choice at that position, is scheduled to miss MLS action while with the U.S. under-23 national team at the Olympic qualifying tournament this spring and, if the Americans advance, the Summer Games in London.

Dudar is the fifth player acquired since the end of last season, joining right back Robbie Russell, (from Real Salt Lake), midfielders Nick DeLeon (first-round draft pick) and Danny Cruz (from Houston), and forward Maicon Santos (free agent). United has also been pursuing an international striker, but it’s unclear whether the club will sign anyone before the season commences on March 10.

This description of Dudar by a European technical director was just relayed to me: “Dudar is an experienced, physically strong defensive leader with one of the best long balls I have seen. Good player!”