*D.C. United has a dark history with concussions. So before finalizing a contract this winter with Argentine center back Emiliano Dudar, who had suffered a serious head injury in September 2010, the club put him through a series of tests. He passed him them all, and now is slated to start on the backline. Read my profile of the 6-foot-4 defender and the frightening details of his injury. (The story appeared on the front of the Sports print edition — page image here).

A few leftover notes that didn’t make it into the story:

Dudar said he also weighed offers from Germany and Austria before signing with United.

His father Roberto, an administrator in the Argentine train system, is a rarity in Argentina — he doesn’t care about futbol, though he has a casual interest in Boca Juniors. Dudar’s mother Ana Maria is a River Plate supporter and a futbol fanatic. “My mother probably knows more about football than me,” he said. His sisters are also River fans. The family is from the Caballito neighborhood in central Buenos Aires.

As a kid, Dudar’s favorite players were Brazilian attackers. Oh, he also liked Diego Maradona.

Before joining United, he’d been to the United States for his honeymoon (Miami) and to visit relatives (New York/New Jersey).

He doesn’t speak much English but said he has purchased a language program and insisted his bilingual teammates speak to him in English, to accelerate the learning process.

What’s he like off the field? “He’s a cool dude,” teammate Ethan White said.

*United will play its second match at the Carolina Challenge Cup against the tournament host, the third-division Charleston Battery, on Daniel Island tonight at 7:15 p.m. D.C. United’s Web site will provide live streaming video. (Lower your viewing expectations: It’s one camera from a distance.)

Bill Hamid and Perry Kitchen are with the U.S. under-23 national team for tonight’s friendly against Mexico at FC Dallas Stadium (10 p.m., Telefutura). Kitchen celebrates his fifth birthday today; born on a leap year, he is actually 20.

*Andrew Dykstra’s signing this week filled out the goalkeeping corps. He joins Hamid and second-year Joe Willis, who stopped a penalty kick Saturday against the Chicago Fire.

“We’re lucky to have him,” Coach Ben Olsen said. “Dykstra has game experience in this league, so it’s nice to have him part of the crew. He’s competing for playing time because he wants to play in real games and we know he can.”

Dykstra, 26, started 17 league matches for the Fire in 2010 before being waived last winter. He moved to Charleston last season and had a 0.98 goals-against average, best in the USL Pro division.

“My family is very happy about the move to D.C., especially my mother,” he said, laughing.

Dykstra has deep ties to the Washington area: He was raised in Woodbridge, Va., and played at Osbourn Park High School and Virginia Commonwealth University.

“I was in the fifth grade doing birthday parties at RFK Stadium,” he said. “I remember watching Jeff Agoos and Eddie Pope and all of those guys when the league started. It’s kind of strange belonging to the same club as they did. It’s a little weird when I think about it.”

With a newly acquired German passport — his mother’s parents emigrated -- Dykstra pursued European opportunities this winter. He had informal workouts with a few Scottish clubs, a formal trial with Dunfermline and a brief tryout with German Bundesliga side Nurnberg.

With the EU pass, “it’s just nice to know that I have other options outside the U.S.,” he said. “But right now my focus is here.”

*Although United has yet to announce a new contract with Comcast SportsNet, the regional outlet’s online listings show the club’s season opener next Saturday night against Sporting Kansas City appearing on CSN+. (The Washington Wizards are on the regular channel.)