Left back Daniel Woolard, D.C. United’s most consistent defender this season, will miss Saturday’s MLS match at Sporting Kansas City after suffering a concussion over the weekend. The club hasn’t set a timetable for a return, but a neurologist who examined him Monday is optimistic Woolard will be able to resume workouts soon, United officials said.

Woolard, tied for second on the team with 20 starts in 21 games, was injured in the second half of the 1-0 victory over the Columbus Crew. He and teammate Emiliano Dudar knocked heads in United’s penalty area, forcing him out of the match within moments.

“We’re in a holding pattern with him to make sure we go through all the steps to ensure his safety,” Coach Ben Olsen said.

United has had a troubling history with concussions, an injury that has led to premature retirements in recent years.

“We’ve had so much practice with it, we’re probably as well versed as any team in the league with this stuff,” Olsen said. “It’s not a perfect science, though, and each case is different. It’s a bad part of the game that seems to be happening more and more. The protocol [for a return] is getting more specific and better, and the research, and that’s a good thing.”

Meantime, Dwayne De Rosario, who injured a shoulder in a hard fall against the Crew, didn’t practice Tuesday but should be able to play against Kansas City. “It’s sore. I don’t think it’s anything that is going to keep him out,” Olsen said.

Midfielder Andy Najar returned from Olympic duty with Honduras and seems certain to travel to Kansas City. With Woolard out and Robbie Russell recovering from a foot injury, Najar might end up starting at right back and Chris Korb moving to the left from the right.

Najar has filled in on the backline at times this year.

“He looked good and fresh,” Olsen said after practice. “We will be smart with him: It’s still an emotional ride.”

Said Najar: “I am thrilled for what the team was able to accomplish in the Olympics [by reaching the quarterfinals]. I am also grateful the coach gave me the opportunity to play a couple games.”

Najar started the first three matches but didn’t appear in the 3-2 quarterfinal loss to Brazil on Saturday.

“Those are just things that happen,” he said. “I’m not really looking for an explanation.”

Najar, at 19 the second-youngest player on the Honduran roster, reportedly attracted interest from English Premier League clubs.

“I get very happy when I hear that because it’s always been a dream of mine to play in Europe. If the opportunity comes, I will just make the best of it.”

As for United’s frontline, Olsen seems happy with newly acquired Long Tan, who beat out Maicon Santos and Hamdi Salihi for the starting job last weekend.

“Right now Tan’s work off the ball has really helped us. It’s something we need on the field right now,” Olsen said. “That’s not to say the other two don’t have qualities I am going to need for a different game or different period of the season, but right now Tan’s busyness has helped us.”

Salihi, United’s second-highest paid player, wasn’t included on the game-day roster — a conspicuous absence given his salary and the expectations surrounding his arrival in preseason.

“He is healthy, he is fine, he’s playing well, it’s just I have to evaluate 18 players [for the game-day roster]. If I had 20, no problem, but there are always going to be one of two guys that are left off that are doing fine and you could use in a game,” Olsen said. “That’s a good part of where we are with our depth. ... [Against Columbus,] I just thought the game was going to neeed Maicon late and I needed some reserves in other spots.”

That said, veteran Josh Wolff, a player-assistant coach, also made the 18 ahead of Salihi. Olsen said the decision was based on positioning: Salihi, Tan and Santos are target forwards, while Wolff plays in a withdrawn role and, if needed, could step in for De Rosario.

Andrew Dykstra, United’s third-choice goalkeeper, remains on loan with the third-division Charleston Battery