D.C. United has reached the midway point of training camp, three weeks down and three weeks to go until the March 3 opener against MLS Cup champion Atlanta at Audi Field.

The roster has taken shape with the arrival of a much-needed right back, but there remains an inescapable vacancy in the front-line corps, some concern about the back line and a general need to fill several openings.

The organization weathered a transfer storm involving its exciting central midfielder, but now contract issues with that playmaker have moved to the forefront and, without a resolution before Opening Day, could end up causing a distraction.

In the big picture, though, Coach Ben Olsen seems happy with where things stand. The foundation of his team, which went on an almost-spotless run down the 2018 regular-season stretch, has returned. And unlike most years, United does not have to jury-rig the roster before becoming whole during the summer transfer window.

After a weekend break back home and indoor training for two days, United will resume workouts in Florida this week and prepare for three friendlies: second-division Tampa Bay Rowdies on Saturday, the Philadelphia Union on Feb. 20 and the Montreal Impact on Feb. 23.

Here are a few things on Olsen’s mind:

1. Who is Wayne Rooney’s backup? At the moment, there is no natural option. When the English striker exited the preseason opener with a bruised right shin, a rookie seeking a contract entered. Five days later, with Rooney sitting out until the second half, midfielder Ulises Segura stepped in.

Rooney was a warrior last year, playing all but 159 minutes in a 20 game rush over three-plus months. He cannot be asked to maintain that pace over the course of a full season, one in which will involve much more travel than during the home-heavy stretch late last year.

Darren Mattocks was a nice option last season, taking advantage of tiring defenses with his pace and athletic ability. He grumbled about playing time, however, and ended up joining expansion Cincinnati this winter.

United did not have any genuine candidates in camp during the first stage of camp, and with time running short, the search is becoming urgent.

2. Is Luciano Acosta happy? United is juggling two delicate issues regarding the Argentine maestro: the failed transfer talks with Paris Saint-Germain and the expiration of his MLS contract next winter.

Since arriving in 2016 at age 21, Acosta has had some tempestuous moments. The events that triggered him — being substituted and being the recipient of nasty tackles — were mild compared to the disappointment of a life-changing move to a major European club falling apart.

Acosta did not pout, at least not publicly. He returned from France right away, rejoining his teammates for the first friendly — although Olsen rested him — and scored 21 minutes into the second match.

The initial reaction suggests he is committed to United’s cause. And by doing so, he could better position himself in the eyes of European suitors.

Meantime, United remains in talks with Acosta’s agent about a long-term contract that would make him among MLS’s highest-paid players. Such a deal would not prevent United from fielding offers from abroad, but it would ensure both a happier Acosta and a lucrative transfer fee if a move surfaced.

Without a new pact, United would be in danger of both losing Acosta and not collecting a penny next winter. Players are allowed to sign a precontract with a new team within six months of a contract expiring.

3. Does D.C. need another center back? It’s not as high of a priority as a second forward, but club officials say they are in the market. Steve Birnbaum is a sure starter after a strong 2018 campaign, and with Kofi Opare gone, Frederic Brillant is the only other experienced option.

Brillant will turn 34 this summer, and neither he nor Birnbaum is particularly mobile.

United has high hopes for Donovan Pines, who left the University of Maryland a year early to sign a homegrown contract, but he will need time to adapt to pro demands. Jalen Robinson needs to have a breakout year after 14 starts the past three seasons.

4. How does United want to play? With most of the starters returning, Olsen has retained a 4-2-3-1 formation in preseason. In workouts, he has emphasized initiating attacks from deeper positions, starting at the back line and circulating the ball through midfield while utilizing overlapping outside defenders.

Greater attacking diversity would ease the pressure on Acosta and Rooney making things happen.

5. Will Loudoun United sign any players? A month from the debut of D.C.'s second-division team — which is designed to improve long-term player development — there is still no one officially on the roster. Look for young players in D.C. camp, academy prospects and a few outsiders to make up Richie Williams’s squad.

There’s still no word on the location -- or multiple locations -- of the first six home games, though the likely site is Audi Field, a temporary solution until a 5,000-seat stadium opens in August in Leesburg. The team is also in talks with George Mason University.