For most of a soggy evening at RFK Stadium, it was difficult to tell which team was locked in a tense playoff chase and which was playing another inconsequential match at the end of a dreary season.

D.C. United, flirting with the worst record in MLS history, was pretty darn good Saturday night against the Philadelphia Union. But after Nick DeLeon provided the lead with a searing shot late in the first half, United failed to seal the outcome. And typical of a campaign that has gone wrong in almost every conceivable way, D.C. conceded Jack McInerney’s equalizer in the 90th minute to finish in a 1-1 draw before an announced crowd of 11,213.

Winless in league play since Aug. 3, United (3-22-7) must win its final two matches to avoid equaling or setting the mark for fewest victories since MLS launched in 1996.

D.C. was the better side for most of the match but ended up scoring fewer than two goals for the 29th time and extending its winless streak in league play to 10 (0-7-3).

“The fact we didn’t finish that game off is pretty amazing,” Coach Ben Olsen said. “You let teams hang around like that and you don’t get the second or third or fourth [goal], eventually they are going to throw enough [players] forward that they are going to get balls in the box and something can happen.”

That is what happened in the dying moments. Jose Kleberson swung a cross to McInerney on the back side for an eight-yard header, his 11th goal of the year but first since June 1 for the Union (12-10-10).

To that point, United was sharp defensively and manufactured quality chances.

DeLeon shattered the deadlock in the 36th minute with a rasping drive from 30 yards that beat former University of Maryland goalkeeper Zac MacMath to the far upper corner for his second league goal of the year.

The Union had offered room, and DeLeon seized it.

“They dropped off, I had the space and it’s just one of those hits that feels good when it comes off your boot,” said DeLeon, who departed in the 70th minute with a hip flexor injury that limited his training time during the week.

After United’s Bill Hamid made a leaping save on Conor Casey’s header, D.C.’s Conor Doyle hit the right post from the edge of the penalty area and Luis Silva missed a clear one-timer from 10 yards. A minute into the second half, MacMath made a leg save on Lewis Neal’s bid.

United certainly should have sealed it in the 83rd minute. MacMath strayed out of the box to challenge Doyle on the counter, but after rounding the keeper, the D.C. striker was too slow to shoot, allowing MacMath to execute a slide tackle from behind. The ball slipped to Chris Pontius, who, with MacMath stranded in the middle of the box, fired high from 18 yards.

Seconds later, Hamid preserved the lead with a superb one-on-one save on McInerney.

With time running out, though, the Union’s pressure paid off.

“We had the chances,” Doyle said. “We could have finished them off. It’s frustrating not to do it.”

United notes: Captain Dwayne De Rosario is on Canadian national team duty ahead of Tuesday’s friendly against Australia in London and was not available Saturday. . . . Defender Ethan White will miss the final two matches with a calf injury, the club announced before the game. Dejan Jakovic (adductor) and midfielder John Thorrington (calf) are also done. . . . Union midfielder Brian Carroll (West Springfield High) made his 300th regular season appearance.