The single bad experience etched in Alan Green's memory of his first trip to the United States two years ago is an 8-2 shellacking the Diplomats absorbed at the hands of the then not-so-powerful New York Cosmos.

"It was the worst score ever for me," said the 5-foot-7, 145-pound forward. "But I expected to lose to them. You can't kid yourself. It's difficult to do anything when you're on a bad side (team)."

Green was one bright light in a woeful (10-16) Washington team that year. The Englishman led the Dips in shots (61), goals (nine), assists (five) and total points (23). Because of injuries, he played only 16 games.

Green will get another shot at the Cosmos here Sunday.

"I remember him being a good player when I coached against the Dips," said Washington Coach Gordon that time. "That's why I went after him when I came to Washington last year."

Bradley's two-year effort to obtain Green's contract from Conventry City in England ended last month when the elusive forward, somewhat disenchanted with his lack of playing time, decided to sign again with Washington.

"My coach (Gordon Milne) and I had differences of opinions about my play," said Green. "I felt I was playing well but I couldn't get on the First Division team. I decided to break away."

Bradley and the Dips, who remember Green's long runs into the box for goals in '77, are glad he did.

"His main asset is quickness," said midfielder Jim Steele. "He makes us feel confident we're going to score."

Green, who practiced only one day with the Dips before starting against Fort Lauderdale opening day two weeks ago, had some problems getting into the flow of the offense that day. He took only four shots but did get credit for an assist on a Bobby Stokes goal in the Dips' 2-1 victory.

"He had to adjust to our style and pace of the players," said Bradley. "He's a fine player and I wasn't worried about his slow start. I knew he'd fit in. He has been a goal scorer from day one and we expect him to score goals."

Green exceeded Bradley's expectations last Sunday against Atlanta. The darting, bearded winger was all over the field and, had he not been a step too far to the right or the left on several occasions, may have established a Diplomat single-game scoring mark of three goals.

He took eight of Washington's mind-boggling 31 shots on goal and scored twice in an easy 5-1 victory.

"It's a matter of getting to know the people out there," said Green, who again practiced very little last week because of business in England. "You get more comfortable each game. I haven't set any big goals for myself except to do a bit better than I did in '77."

When striker Paul Cannell, almost completely recovered from a leg operation, returns to the lineup, Green should be even more effective. Cannell is especially dangerous on high balls and will draw much of the attention from the defense. Green and his lookalike, Stokes, should then be free to play loose balls off Cannell.

"We're small and we can't play the high balls. But when Paul cames back, Bobby and I can feed off the knock-downs," said Green, "We should do well together."

Washington's offense, even with Green still feeling his way, has been smooth. The Dips have outshot their tow opponents, 52-19, totally controlling the tempo.

The Dips will get their first major test of the young season Sunday when they host the Cosmos at RFK Stadium at 2:30 p.m.

Green says he doesn't remember much about the Cosmos except that "(Franz) Beckenbauer, (Carlos) Alberto and (Giorgio) Chinaglia are still there, Pele is gone and the Cosmos are champions."

Diplomat defender Robert Iarusci, who played on the Cosmos' two NASL champion teams, suffered a slightly sprained ankle during practice yesterday. Bradley said Iarusci's status for Sunday will be on a day-to-day basis.

Defender Tommy O'Hara, who injured his shoulder in Sunday's game, is listed as probable.

Midfielder Joe Horvath is the Dips' leading scorer with six points and Green is right behind with five.