The first time Franz Beckenbauer, the Cosmos' midfielder, laid eyes on Gerd Mueller, he chuckled to himself.

"He was so short and squatty, I wondered how he would ever score a goal," Beckenbauer said with a smile. "He didn't look like a goal-scorer."

Despite running around on legs that look like tree trunks, "Der Bomber" went on to become one of the greatest scorers in German soccer history. He was a seven-time scoring champion in the German First Division and made 62 international appearances for his national team. The 5-foot-10, 170-pound Mueller, who will be 35 in November, showed he hadn't lost his touch after he joined the Fort Lauderdale Strikers last year, setting a club mark of 55 points. This season Mueller was not as effective scoring only 36 points on 14 goals and eight assists. Howover, he is still one of the most dangerous strikers in the league.

"He (Mueller) just hangs around the goal, walking around whistling," said Cosmos defender Jeff Durgan, who will most likely be assigned the task of stopping Mueller in Soccer Bowl '80 Sunday at RFK Stadium. "Then he scores a brilliant goal to beat you. You have to stay on him for 90 minutes." s

If the Strikers, who finished 18-14 on the season and will be making their first appearance in the NASL championship game, plan to make a game of it with the powerful three-time league champion Cosmos, Mueller will have to be effective. Team captain Ray Hudson (11 goals and 18 assists), Teofilo Cubillas (14 goals, 14 assists) and Mueller are the main scoring threats for Fort Lauderdale.

The American Conference Eastern Division runners-up use a 4-4-2 alignment, taking advantage of talented midfielders.

Mueller plays up front with Steve Ralbovsky, a deceptive winger who played with Colorado, Chicago and Tulsa before joining the Strikers last season. The winner of the Hermann Trophy (most outstanding player in college) while at Brown University, Ralbovsky scored one goal and had six assists.

Hudson, Cubillas, Lex Schoemaker and Francisco Marinho, formerly of the Cosmos, are quick, explosive and experienced enough to give the NASL "glamour boys" trouble.

Hudson, a crafty technician who had four game-winning goals, including the winner in the final minigame to knock out San Diego, stabilizes the middle. Cubillas is a flashy one-on-one artist with either foot. He turned in a hat trick to help the Strikers whip the Cosmos, 4-1, in their first regular-season meeting. Schoemaker, a physical type with surprising speed, made eight goals and 13 assists this season.

Marinho, a tempermental sort, missed, one-third of the season with a shoulder separation. But he is an offensive midfielder (three goals, five assists) and Coach Cor van der Hart may decide to go with a defensive-oriented player. Colin Fowles and Ken Fogarty, both good defenders, could be used in the midfield if needed.

The Striker defense has had problems. Injuries to key people and van der Hart's tendencies to use different players at times often led to breakdowns. The team gave up 55 goals during the season, compared to the Cosmos' 41. The back line, along with goalkeeper Jan van Beveren, was much more aggressive in the playoffs and allowed but 11 goals in nine games, including seven in two games.

Van Beveren, an honorable memtion all-NASL player, joined the team in midseason and finished with a 1.78 goals against average and two shutouts. He was superb in the playoffs, blanking three opponents.

Anchoring the back line is stopper Roy Wiggemansen, a 21-year old South Afican who was recently installed in the lineup and played well in the playoffs. Jon Pot, who edged out Hudson for the iron man award (most minutes in the regular season), along with Fogarty, will have their hands full keeping up with Giorgio Chinaglia. Fogarty marked Chinaglia in both regular season contests but sprained an ankle in the San Diego playoff game and may not be at full strength.

Fowles and Arsene Arguste are both capable defenders who could step in for Fogarty. Fullback Tibor Gemeri, a finesse player who is good in the air, started all six playoff games and will probably be in the starting lineup Sunday.