Capitals winger Alex Ovechkin is upended by Devils defenseman Anton Volchenkov. (Toni L. Sandys/THE WASHINGTON POST)

Two weeks ago General Manager George McPhee singled out frequent, unnecessary penalties as the single most damaging problem for the Washington Capitals in their sluggish start. Thursday night in their latest loss, they showed that they still haven’t found a way to eliminate the flaw.

The Capitals entered the third period with a one-goal lead, but five consecutive penalties in the span of 7 minutes 56 seconds derailed their efforts and paved the way for a 3-2 New Jersey Devils victory at Verizon Center.

While some of the calls may have been debatable — several players questioned the validity of the rash of minors they were whistled for in the third — the Capitals simply cannot afford to continue taking this many penalties. This defeat dropped the Capitals (5-10-1) back into last place in the NHL and whether the penalties were real or imagined, it’s costing them valuable points.

“I thought maybe a couple of calls are tough calls,” Coach Adam Oates said, calling a tripping penalty on Alex Ovechkin into doubt. “But bottom line is that’s too many. It’s been too many times.”

Washington held a 2-1 lead at the start of the third thanks to goals by Mathieu Perreault and Mike Ribeiro, but less than three minutes into the final period their parade to the penalty box began. Grinder Matt Hendricks went off for holding New Jersey star winger Ilya Kovalchuk 2:55 into the third, and while that penalty alone might not have been problematic, officials called Washington for delay of game 14 seconds later, after Jay Beagle shot the puck over the glass.

The Post Sports Live crew debates whether there is room for optimism following a week that saw the Capitals win three of four. (Post Sports Live/The Washington Post)

It marked the eighth such minor penalty the Capitals have been called for this season, but there was some uncertainty as to whether it would actually be a penalty. The referees explained that although the puck landed in the Washington bench it was a penalty because it arced over the top of the glass and the crowd en route to its final destination.

“I didn’t know that rule. So that’s what the linesman had explained to me,” Beagle said. “Two of the refs had no clue. So one linesman was just kind of making that call. And I could hear them talking. And they were like ‘We didn’t see it.’ ”

Rookie Tomas Kundratek served the penalty that gave the Devils more than a minute and a half of a five-on-three advantage. Penalty killers Karl Alzner, John Carlson and Beagle, who eventually swapped with Nicklas Backstrom, managed not to allow a single shot on goal during that deficit.

“The first five-on-three, we did a good job there and then they just got another one right away after,” Backstrom said. “It’s frustrating and we talked about it before we went out for the third period, too. We’ve got to be more disciplined, it’s not good enough.”

Less than two minutes after the Caps thwarted the two-man advantage, though, Ovechkin went to the box for tripping Alexei Ponikarovsky, sending the penalty killers back over the boards. They managed to kill off that one, too, but 27 seconds after it expired, the Devils scored to make it 2-2.

Devils center Andrei Loktionov beat Ribeiro on a faceoff and then drove to the net for a rebound goal when a point shot by Adam Larsson popped out to the right of the crease.

Washington’s trips to the penalty box weren’t over yet. Forty seconds after Loktionov evened the score, John Erskine was whistled for hooking Patrik Elias, who had scored New Jersey’s first goal of the contest.

Tom Poti followed Erskine to the box all of 52 seconds later for an interfering with David Clarkson, giving New Jersey its second two-man advantage of the game this time for 68 seconds. At that point, Washington’s penalty killers had played the bulk of the period and the Devils’ offensive threats had seen enough of the special teams unit to pick it apart. The Caps’ six penalties in the third were the most they’ve had in a period this season.

With “enough power plays they were bound to score one with the guys they have on the ice. They finally got the look they needed with the guy they wanted to shoot,” Alzner said. “It was pretty deflating. After the first five-on-three kill we had some energy, but we went right back to the kill again.”

Nineteen seconds remained in New Jersey’s second five-on-three when Kovalchuk blasted a one-timer from the point through traffic that goaltender Braden Holtby (34 saves) never saw 11:40 into the third. Kovalchuk’s goal stood as the game-winner and reinforced a message Oates has been preaching since the season opener: Washington can’t allow penalties to compound and cost them the game.

“How many times are we going to have this conversation?” Oates said. “It’s on us.”