D.C. United’s Perry Kitchen, right, will miss Sunday’s game against Colorado. Kitchen will miss his second consecuitve United match while playing with the U.S. under-20 national team. (Ned Dishman/GETTY IMAGES)

D.C. United devoted much of the winter to reworking the defensive corps. Three matches into the MLS season, with three starters absent and a robust Colorado attack waiting, Coach Ben Olsen’s new group will confront a sizeable test.

“It’s definitely frustrating to have to interchange so many guys, but at the same time, we feel we are deep enough to handle it,” captain Dax McCarty said ahead of Sunday’s match against the defending champion Rapids (2-0) in Commerce City, Colo.

Perry Kitchen and Dejan Jakovic, who formed a strong central partnership in the season-opening victory two weeks ago, are in Guatemala City and Washington, respectively. Kitchen, on extended duty with the U.S. under-20 national team, will miss his second consecutive match, while Jakovic is serving a one-game suspension after receiving a red card in last weekend's loss at New England.

Right back Jed Zayner is recovering from a hamstring injury suffered in the first game and isn’t expected to play, leaving left back Marc Burch as the only holdover from the opener.

Olsen will likely fill the holes with Uruguyan newcomer Rodrigo Brasesco and Daniel Woolard, a natural left back, in the middle, and rookie Chris Korb on the right side for the second straight match.

Among the other defenders on the roster, veteran Devon McTavish remains sidelined with concussion symptoms, and Ethan White and Conor Shanosky lack the experience to confront a Colorado attack that has scored at least three goals in five of the past seven home games . In addition, the Rapids have lost at their suburban Denver venue just once in 15 matches (last October to United).

“It’s still a group, it’s still 10 guys out there working together to defend,” Olsen said of the lineup in front of goalkeeper Pat Onstad. “We feel comfortable with whoever we put out there.”

No team, though, is comfortable facing Colorado’s Conor Casey and Omar Cummings, who teamed for 27 league goals in 2010 and fashion one of MLS’s most menacing front-line tandems. Casey, a bruising target man, has been hindered by a calf injury while Cummings is returning from Jamaican national team commitments.

They are no doubt drooling at the opportunity to exploit United’s weakened backline and a defensive midfield that might be without Clyde Simms (calf) for the second consecutive match.

Brasesco started for Kitchen in the second game, but Woolard has yet to play. In preseason, Woolard nearly beat out Burch for the left-side job. He didn’t serve in the middle during training camp but does have prior experience there. Kurt Morsink is the primary option to replace Simms for the second straight week.

Olsen described Casey as “a beast. He’s got good feet for a guy his size [6 feet 1] and he makes good decisions. Cummings stretches defenses, which allows others to benefit from his speed.”

United’s backline was exploited early in the 2-1 loss to New England, allowing a long ball to drop into space. Although a handball should have nullified Zack Schilawski’s goal, the sequence didn’t sit well with Olsen and Onstad, the 43-year-old goalkeepers coach pressed into service because of injuries.

“If we come in like we did in the first 25 minutes against New England and don’t have any energy,” Onstad said, “it’s going to be a very difficult game for us.”

Onstad’s experience has helped ease the transition with the new group of defenders, but in the coming weeks, he expects to yield the starting job to Bill Hamid. After months of rehabilitation from shoulder surgery — and appearances in two reserve matches — the 20-year-old Hamid has begun to find his form.

“Bill is getting closer and closer,” Onstad said, raising the possibility that Hamid will start Wednesday against the Philadelphia Union in a U.S. Open Cup qualifier at Maryland SoccerPlex. “The big thing is to get Bill up to speed, and he’s pretty darn close.”

Another goalie, Steve Cronin, is ahead of schedule in his return from a broken wrist and soon will challenge Hamid for playing time.

For now, the primary focus is the backline.

“This is kind of good for our team — these guys who haven’t played much getting some time,” Zayner said. “This league is all about depth and we’re going to prove to be a good team when we have awesome depth everywhere. We have it in midfield and forward, and now we need it on defense.”