After seven games, Coach Bryan Murray is wondering how his Washington Capitals, who led the National Hockey League in penalty killing a season ago, could slip so far that they now rank last in that department.

Murray is not losing sleep over the puzzle, however, no doubt because he is able to recall that at the seven-game mark a year ago, he was faced with a far more serious problem. At that time, the Capitals were 0-7.

Although the current 2-3-2 record beats 0-7 on any scale of progress, it is hardly the getaway the Capitals were expecting. The principal reasons are foolish penalties and the inability to kill them off.

Over the seven games, Washington has yielded 12 goals in 36 power plays for a 66.7 defensive success ratio, compared with last year's 86.7 mark that was the NHL's highest in five years.

Over the full season, should this rate of failure continue, Washington would give up 137 power-play goals. The NHL record is 110, by the 1982-83 Pittsburgh Penguins.

In the last three games, of which the Capitals have salvaged one point of a possible six, they have given up 14 goals, with nine coming in extra-man situations.

Murray spent much of Friday's practice in Calgary working on special-teams drills and he repeated that procedure here today. He did not make any changes in the penalty-killing unit.

"I'm really not able to change the personnel and, anyway, I think we proved last year the personnel are right," he said. "I'm leaving (Glen) Currie, (Bob) Gould and (Doug) Jarvis up front and I expect them to straighten things out. The principal problem is that they're not putting much pressure on the puck in the neutral zone.

"Once the other teams have been permitted to organize across our blueline, they seem to be scoring very quickly. We've played a couple of teams with very good power plays, and that's got to be one factor, but we're not playing aggressively, the way we did."

Calgary, which scored on three of four opportunities Thursday in beating Washington, 5-3, took the NHL's best power play, 34.2 percent, into tonight's game at Toronto.

Part of the Capitals' problem, of course, is the absence of Gaetan Duchesne, a tireless penalty killer in tandem with Jarvis. Duchesne suffered a broken left hand in the opener at Philadelphia and has not played since.

"I know he's valuable," Murray said. "His skating ability and quickness are a big factor. We have to play somebody like that with Doug to make it an aggressive type of system."

Gary Sampson and Bryan Erickson have been used with Jarvis. Whereas Currie, Gould, Jarvis and Duchesne did most of the penalty-killing work a year ago, Duchesne's absence and the frequency of some of the penalties that have piled up on Washington have prompted Murray to use others, like Bob Carpenter and Craig Laughlin, in shorthanded situations.

If Murray tends to be diplomatic about the penalty killers' shortcomings, they get no such kid-glove treatment from goalie Pat Riggin, whose otherwise sturdy goals-against average has been inflated by the extra-man scores.

Asked if he was impressed by Calgary's power play, Riggin replied, "I don't give them any credit. Our penalty killing has just been terrible."

There is no argument from the disappointed penalty killers themselves, although all are convinced they can turn it around.

"We've been breaking down and panicking, things that are not in character for us," Jarvis said. "But part of it is the situations we've been caught in."

The Rangers scored three times during a five-minute major to Alan Haworth, which came shortly after Washington had killed off back-to-back minor penalties, leaving the principal penalty killers tired.

In Calgary, while Gould and the Flames' Eddy Beers served double minors, Washington was hit by foolish offensive-zone penalties against Dave Christian and Scott Stevens. In each case, Calgary quickly converted the four-on-three opportunities.

The Vancouver Canucks, Washington's opponents Sunday (Home Team Sports, 10 p.m.), are hardly in the class of the Rangers and Flames, so the Capitals have a chance to recoup their sagging fortunes.