For the past six weeks, Mike Lampman has been watching the Washington Capitals from the press box, a most uncomfortable spectator with a flexible cast supporting his neck.

Tonight, when the Montreal Canadiens visit Capital Center at 7:30, Lampman will be absent. He will undergo surgery this morning at Arlington Hospital, his season over and his career in doubt.

Lampman suffered abnormal slippage of the fifth and sixth vertebrae on Dec. 3, when he was rammed into the boards by Philadelphia's Moose Dupont. The cast was utilized in the faint hope of avoiding surgery, but it proved unsuccesful.

"An examination showed that the vertebrae had slipped further," said Dr. P. M. Palumbo Jr., the Capitals' team physician. "We felt it best to stabilize the vertebrae with fusion. Barring further complications, he would be able to play next year."

Palumbo said Lampman would need to wear a brace for eight to 12 weeks, depending on the rate of healing. The operation consists of placing the vertebrae back in position and fusing them with a boen graft.

"I'm pretty upset about it," Lampman conceded. "I kind of can't believe it.My neck felt good enough to play, but the X rays took care of that.

"I don't think there'll be any trouble with the operation. Dr. Palumbo thinks I'll be 95 per cent after it. The idea of 12 weeks in that thing isn't pleasnat, but I'm a lot more upset about not being able to play this year.

"There's always the next year, that's what keeps you going. I don't think we're out of the playoffs this season at all, and next year we'll be even better."

General manager Max McNab is another who is most optimistic about the Capitals' playoff chances, and he took a step to reinforce them by signing veteran goalie Roger Crozier. The 34-year-old Crozier, who last played for Buffalo in December, 1975, began workouts with the Capitals yesterday.

"We want to make the playoffs," McNab said. "That's our whole objective. We'll do anything to realize it. Crozier is a proven guy and we know he can do the job if anything happens to the others.

"We were concerned before, when Bernie Wolfe was sick, about being caught short. If we should run into another Wolfe incident and if Ronnie Low stopped one, we're just not confident about the men on the farm."

The club's agreement with Crozier calls for him to work out several weeks to determine whether he can play. If not, he will assist the youngsters in the farm system.

McNab also has an eye on another goalie, Lou Levasseur. A first-team World Hockey Association all-star selection for the disbanding Minnesota Fighting Saints, Levasseur was among seven players sold to Edmonton last week. He is on the Capitals' negotiation list.

"Dave Keon [another of the seven] still has some hockey left," McNab said. "He is Toronto property and we have discussed him with the Leafs. And Crag Patrick [future undetermined] was their best player for a while before he got hurt. I've always liked him.

"But we can't talk to any of them until the Toronto office of World Hockey verifies that they are free agents with Central Registry. Right now the players claim they're free agents because they weren't paid, but the league says no."

Today is judgment day for right wing Bill Riley, who completes his 10-game NHL trial against the Canadiens. Afterward, McNab must either sign the 26-year-old Riley to a pro contract or return him to Dayton of the International League.

"He will definitely play tonight," McNab said. "We are still evaluating his situation. He's helped us, no doubt about."

Apparently, a key factor is the progress shown by Blair Stewart, who has played six games with Springfield of the American League following recuperation from a broken right leg suffered Nov. 7. Riley and Stewart are similar types, aggressive and hard working but unpolished in the shooting and passing phases of the game.

Tonight's contest is the 15th between the teams and Montreal has won all 14 previous meetings. Earlier this year, the Canadiens scored a 6-0 triumph at Capital Centre and a 7-2 decision at Montreal. The latter game on Jan. 8 is the only one among their last 10 in which the Capitals have allowed more than three goals.

Montreal boasts the NHL's best power play, with 38 goals in 133 advantages, a 28.6 per cent conversion rate. The Capitals, last in that area with 9.4 per cent, have moved up to No. 6 in penalty killing by going through 11 straight games without permitting an extra-man score.

Right wing Guy Lafleur of the Canadiens leads the NHL in scoring with 36 goals and 36 assists for 72 points. Steve Shutt, who patrols the left side of that superb line with Jacques Lemaire at center, ranks third with 62 points,two fewer than Los Angeles Marcel Dionne.