With only two healthy center backs and the season days from starting, D.C. United on Tuesday continued its hurt for defensive reinforcement by inviting another MLS free agent to workouts.

Kevin Garcia, 29, joined Jonathan Campbell, 26, at the RFK Stadium training grounds, vying to make an impression and earn a contract.

Steven Birnbaum and Frederic Brillant form the starting partnership, but with Donovan Pines sidelined with an ankle injury, United has no natural back-ups for the opener Saturday against the Colorado Rapids at Audi Field.

The organization is also pursuing help overseas, most notably Mali’s Bakaye Dibassy, but his French club, Amiens, has been unwilling to sell him during its efforts to avoid relegation to the second division.

Campbell made 49 starts in three years with Chicago and started four times for MLS Cup champion Seattle last year. Garcia was with Houston from 2016 through last season, making 21 starts. He also played regularly for Houston’s second-division affiliate, Rio Grande Valley.

Asked whether he is satisfied with his defensive depth, Coach Ben Olsen said: “Yes and no. It’s no secret we are looking to add some depth and competition in the back. We’ve had some bites but we haven’t been able to reel anything in as of yet. I would expect it to come sooner rather than later."

General Manager Dave Kasper said United could sign two defenders before May 5, MLS’s first transfer and trade deadline. That deadline does not pertain to free agents.

Campbell is a center back and Garcia has played multiple positions on the back line. Both are 6 feet 2. Dibassy is adept in the middle and left side.

United’s pursuit of another attacker grew in importance following Paul Arriola’s ACL injury at training camp. And a Norwegian report said United is interested in Ghanaian defensive midfielder Mohammed Abu, who played for Columbus in 2017-18 before moving to Valerenga in Norway.

D.C. officials confirmed Abu, 28, is under consideration.

>> Edison Flores, United’s marquee winter signing, played sparingly in preseason because of a minor muscle ailment and logged just 45 minutes in the final tuneup last Saturday against Philadelphia.

He is almost certain to start against Colorado but seems unlikely to play the entire match.

“We played him 45; he got through that,” Olsen said. “After a full week of training, he is going to be more than that [this weekend]. We are always evaluating it, whether it’s the data or just eyes on him and experience of knowing when a player is fading physically. We’ll use those two to monitor him.”

Yamil Asad, a projected starter who was sidelined much of preseason with a groin injury, played 30 minutes in the preseason finale and doesn’t seem likely to start this weekend.

“Yamil is extremely motivated to get back into the squad,” Olsen said of the Argentine attacker beginning his second tour with United after scoring nine goals in 2018. “He wants to play. He wants to be on the field. We’ll evaluate it this week.”

If Asad does not start on the left wing, Ulises Segura probably will. The Costa Rican had a goal and an assist and drew a penalty kick against Philadelphia on Saturday.

Of choosing between Asad and Segura, Olsen said, “These are good problems.”

>>Birnbaum is expected to resume his duties as team captain after yielding to Wayne Rooney the previous two seasons.

>>Estonian forward Erik Sorga, whose contract is being upgraded to MLS from second-division USL Championship, is expected to receive his work visa this week. He does not need to return home to finalize it.

Without it, he would not be eligible to play in the opener.

>>The proposed friendly between United and Rooney’s Derby County is tentatively slated for Oct. 7, three days after the MLS regular season ends. A formal announcement is possible this week.

>> Weather outlook for the 1 p.m. kickoff Saturday: 39 degrees, sunny, light wind. WJLA 24/7 News will carry the match.

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