In his first major deal as general manager of the Philadelphia Flyers, Bob Clarke dealt veteran center Darryl Sittler to Detroit for youngsters Murray Craven and Joe Paterson. Upon learning of the move, a rival National Hockey League general manager commented, "That's a bad trade. Sittler was the only real leader on the team."

The Flyers, however, uncovered another leader in Dave Poulin, a graduate of Notre Dame signed as a free agent two years ago who had played one season in the NHL.

With Poulin as a dynamic captain, Tim Kerr enjoying his second straight 50-goal season, Pelle Lindbergh winning 37 games in the net and Craven having 25 goals and a plus-40 rating, the Flyers have been the surprise team of the NHL. In the midst of a club-record 11-game winning streak, the Flyers have 103 points, most in the league, in what had been considered a rebuilding year. They are genuine threats to win the Stanley Cup, since defending champion Edmonton has not been able to beat Philadelphia in the teams' last eight meetings.

If Clarke made an astute move in dispensing with Sittler, who has only 10 goals and a minus-16 rating in Detroit, he was lucky in another respect.

Clarke's first choice as coach was Bill LaForge, but LaForge had made a commitment to Vancouver. So Clarke turned to Mike Keenan, another lacking NHL experience.

LaForge lasted a little more than a month, as his advocacy of goon tactics with players not inclined to that approach made the Canucks a season-long noncontender. Keenan has proven himself a masterful tactician.

"If LaForge had gone to Philly, he would have revived the Broad Street Bullies, and they'd be nowhere now," one NHL coach said. "Keenan may not have any charisma, but he's got that team doing a lot of things right."

In a preseason poll of correspondents by the Hockey News, only one of 20 picked the Flyers to finish as high as second in the Patrick Division. The consensus was fourth, with one tabbing them fifth, behind Pittsburgh. Seldom has any group of "experts" been so badly fooled.

On an only slightly lesser scale, the St. Louis Blues have stunned the prognosticators and the competition. The experts also consigned them to fourth in the Norris Division, with not one of the 20 polled listing them first.

The Blues have been on top almost from the start and have the best defensive record in the Campbell Conference. They have few stars, but do have eight players with more than 20 goals. Jacques Demers, who would be a strong candidate for coach of the year except for Keenan's performance, has focused on key divisional games with astounding results. The Blues, after losing their first two games to chief rival Chicago, have gone 18-5-4 within the Norris Division.

The NHL's other notable overachievers are Winnipeg and Los Angeles. Their surge to respectability has turned the once-sorry Smythe Division into the league's toughest.

In contrast to St. Louis, the Jets have prospered despite an inability to handle divisional rivals. Ten of their 27 defeats have been inflicted by Edmonton and Calgary, which does little to enhance their playoff hopes.

It is a sure bet that the Jets, onetime Norris Division residents, would gladly return the $1.375 million they received to switch if they could wrestle instead with the weaker teams in the Norris.

The Kings missed the playoffs the last two seasons and seemed destined for a similar fate after their 0-6-3 start this season. However, Pat Quinn's patient coaching has made them an above-.500 club in a difficult division.

Unchallenged leader of the underachievers is Minnesota, the majority choice to finish first in the Norris Division. The North Stars, with Coach Bill Mahoney cast off en route, are struggling with Detroit for third place.

The North Stars' demise since reaching the Stanley Cup final in 1981 is one of hockey's great mysteries. Not only does Minnesota seem blessed with considerable talent, it has managed through Lou Nanne's wheeling and dealing to maintain a flow of high draft picks -- first in 1983 (Brian Lawton) and second in 1982 (Brian Bellows).

What the North Stars have lacked is stability in coaching and playing personnel. But the scoring collapse this season is inexplicable, with only New Jersey and Toronto weaker offensively.

Consider the best NHL goal-scoring mark and production of Dennis Maruk (60-17), Dino Ciccarelli (55-13), Steve Payne (42-27), Bellows (41-25), Tom McCarthy (39-16), Willi Plett (38-13), Neal Broten (38-17), Tony McKegney (37-23) and Keith Acton (36-19). Rarely have so many players hit the doldrums at one time.

It is simpler to place the blame for the problems endured by the other principal underachievers -- Vancouver, the Rangers and Islanders.

LaForge's foolishness put the Canucks so far behind so early that they had no chance to recoup in a division with four clubs over .500. The Rangers had many injuries and became further disoriented by the constant rumors that Coach Herb Brooks -- eventually fired -- was planning to quit at season's end to take a job in Minnesota.

Injuries also wreaked havoc with the Islanders. At one stage, the right side of the defense was gone. At another, only one healthy left wing was available. Coach Al Arbour might have done a better job this year, with the team nine games over .500 despite unceasing adversity, than he managed in some of his first-place campaigns.

Boston, Calgary and Chicago have been disappointing. Still, they are above .500 and headed for the playoffs, so there is opportunity for better things ahead.

Quebec, Montreal, Buffalo, Washington and Edmonton are prospering about as expected, and each must look to the playoffs to make the season a particularly profitable one.

Hartford, Pittsburgh, New Jersey, Detroit and Toronto are struggling, in each case without arousing surprise. They can only hope that a combination of courage and luck will make them the high Flyers of 1986.