Under the best circumstances, the next two weeks promise to test D.C. United’s fortitude and go a long way toward defining the season. But with lingering injuries, another roster change and a scoring rut amid an unsettling stretch, United is entering a trial by fire.

Beginning Sunday against the Philadelphia Union at RFK Stadium, the club will play five matches before Labor Day – the harshest period of the 7 ½-month regular season.

“It’s a huge time for us,” Coach Ben Olsen said after Saturday’s practice. “We could be in better health to get through this stretch, but that doesn’t matter. We have to find a way to make sure we’re picking up points to put ourselves in a good spot. We’ve got to make it work.”

Despite four defeats in six matches, United (11-8-3) remains in good position to secure an MLS playoff berth for the first time 2007. The fact that three of the next four are at RFK strengthens United’s prospects. Since dropping the season opener to Sporting Kansas City, D.C. is unbeaten in 10 straight in Washington, an 8-0-2 surge with 24 goals scored and only eight conceded.

United’s seven-game winning streak at home is the longest in 90-minute outcomes in club history. (The 1998 squad won eight in a row at RFK, but three came in tiebreaking shootouts, a format abandoned two years later.)

Philadelphia (7-12-2) is 2-7-1 on the road with just six goals for. The only multi-goal away performance was a 2-1 victory against the Los Angeles Galaxy on July 4.

United welcomes any factors working in its favor, because others are working against it.

On the injury front, defenders Robbie Russell (foot) and Daniel Woolard (concussion), and forward Maicon Santos (foot) remain sidelined. Reserve midfielder Lewis Neal withdrew from practice Saturday with a groin ailment.

Forward-midfielder Dwayne De Rosario is expected to return from a sore shoulder that forced him to sit out last weekend and playmaker Branko Boskovic should be available after departing at halftime of the previous match.

While United believes it’s well-equipped to compensate for absences, depth will become critical the next few weeks.

“Obviously you are going to run into tired legs and different players will be called upon, but you can generally get a rhythm through these stretches,” said midfielder-forward Chris Pontius, the club’s top scorer with 10 goals. “Hopefully we can get into that rhythm and feed off of it.”

Quickly integrating Lionard Pajoy would bolster United’s hopes. Acquired from Philadelphia on Thursday, the Colombian forward seems likely to start right away. With Santos hurt, Long Tan not up to the task the past three games and Hamdi Salihi out of favor, United needed another option to pair with Pontius or captain Dwayne De Rosario on the frontline.

Pajoy’s role, Olsen said, should alleviate adjustment issues.

“He is in a position where you can pull it off,” Olsen said. “It’s a pretty predictable position. It’s not brain surgery. He knows what he’s doing. Sometimes when you are out wide or in the middle or playing behind the top guy, it can be a little more difficult.”

United needs more production from its pure attackers to complement Pontius, who has scored five of the team’s past eight goals. Salihi and Santos have once apiece in the past eight matches and De Rosario hasn’t struck since mid-May. The slowdown triggered the trade for Pajoy, who has five goals this season but only two in his final 12 appearances (seven starts) with the Union.

To acquire Pajoy, United relinquished hard-charging midfielder Danny Cruz, whose playing time had fallen in recent weeks. His former teammates wouldn’t be surprised to see him in the Union lineup Sunday.

“I told him to take it easy because we know the energy he brings,” McDonald said. “I think he takes five Red Bull [drinks] before he gets onto the pitch, so I’ve had to tell him to calm down, buddy.”