Despite closing out the regular season with four straight defeats, the Washington Diplomats and Coach Gordon Bradley head into tonight's first-round North American Soccer League playoff match in Portland with confidence.

The National Conference match will be televised by WTTG-TV-5 at 11 p.m. It also can be heard on WTOP-AM 1500.

Bradley's optimism centers on the fact that the Dips are as healthy as they have been all season. The only starter missing is Cus Hiddink, who is in Holland working out some contractual problems with his old club. Veteran Gary Darrell, who has filled in admirably at several positions during the season, will retain Hiddink's center midfield spot.

"I feel we can win," Bradley said. "For one we are very fit," and no, we're not despondent because we've lost four straight. We played well. We just couldn't score any goals. And that's the name of the game."

Washington finished the regular season with a 16-14 record and a total of 145 points to capture second place in the Eastern Division, one point ahead of Toronto.

For the Dips to make their second playoff appearance a bit more memorable than their initial showing in 1976 (they lost 2-0 to the Cosmos in a first-round game), they must not allow the offensive-minded Timbers to control play and must score.

Portland has been tough at home, winning 13 or 15 on its artificial playing surface.

Bradley is not as concerned over his club's 2-6 record on such fast, slick surfaces as he is over his inconsistent offense.

"We nearly ran New England and the Cosmos (both 2-1 losses) off the field in the second half," Bradley said. "Our offense wasn't quite as good against Rochester and Toronto."

For Washington to play well, offensively, striker Paul Cannell has to get the ball often.

The feisty Englishman, who has more fouls (103) than he has shots on goal (93) and more yellow caution cards (nine) than any player in the league, has scored only three goals in the last 11 games. He has become a marked man, both by opponents and referees.

"The referees watch Paul all the time. Teams also double-team, him so much it's tough getting the ball inside to him," said Ray Graydon, who leads the Dips in assists with 17.

Graydon and Mike Bakie will blank Cannell up front while Darrell, Henny Van der Ven and Sakib Viteskic will work in the midfield.

The game will feature two teams with contrasting styles. Washington is an aggressive, physical club; Portland depends on quickness and finesse.

Like Washington, Portland will be as fit as it has been in a while. Except for forward Mike Flater, questionable with a twisted knee, the Timers are healthy.

Coach Don Megson rested Flater while the club was losing three of its last five games, in the hope the former Minnesota kick forward would be ready for the playoffs.

In Flater's absence, Clyde Best, Willie Anderson, Stewart Scullion and John Bain have split the scoring duties. Best leads the club with 12 goals and nine assists.

Portland (20-10 and 167 points) finished as the runner-up in the Western Division of the National Conference, 32 points behind Vancouver. The Timbers last appeared in the playoffs in 1975, advancing to the NASL title game losing to Tampe Bay, 2-0. Ironically, Best and Scullion led the Rowdies to victory over the Timbers. Both were obtained by Portland before the '77 season.

The Timbers won't hesitate to attack with as many as eight men, as they did in both previous contests with the Dips. The teams split by 2-1 scores.

"We want to shut down Washington in the middlefield and immediately begin to push everything forward attack," said Megson, in his first season as coach in Portland.

Despite Portland's apparent throwing caution-to-the-wind tactics, the defense, anchored by sweeper Pat Howard and goalie Mick Poole, has yielded but 36 goals. Only Vancouver (29) and Detroit (26) had surrendered fewer goals.

"I expect a hard, tight game," Bradley said, "but I'm confident because our players are fit and ready. We would have preferred to have played them in Washington but . . . since we won't, we'll do our best here."