Although their first regular-season game is Sunday against the Toronto Metros, the Washington Diplomats are still flipping coins and awaiting phone calls to determine what players will fill key positions.

With virtually a skeleton squad of walk-ons, free agents, rookles and a few veterans, the Dips limped through a sorrowful 2-5 North American Soccer League exhibition season. They were blanked, 1-0, by the mediocre Las Vegas Quicksilvers before 3.557 last Sunday at RFK.It was their final tuneup before facing. Toronto, the defending NASL champion, at the stadium at 2:30 Sunday.

"I used the exhibitions to see exactly what we had and get the players in shape," said coach Dennis Viollet, who last year took the club to its best mark, 14-10, and first trip to the play-offs in its three-year history. "We may have played only five or six players that will start this Sunday."

Of the six recruits signed by Viollet on his trip to England during the winter, only Jimmy Redfern and Ken Hill have put on a Washington uniform. Redfern is a speedy winger from third-division club Chesterfield. Hill is a top-notch defender from Gillingham of the third division. They played well in spots in Washington's final two exhibition contests.

Mike Lefter, a forward from the first division's Manchester City and Don McAllister, a rugged defender from Tottenham, began working out with the Diplomats this week. Both should see considerable action Sunday.

Two other English players expected to bolster the Dips' attack, forward Alan Green and defender Graham Oakey, have not been released by Coventry and probably will miss the opener.

"Right now, we have to just sit tight and wait," said assistant coach Alan Spavin. "We know they're coming. It's just a matter of when. Until then, we'll try to get by."

Viollet may have to do some juggling to comply with the league rule that requires each team to have at least six United States citizens, one starter, on its roster at all times.

Midfielders Randy Garber and John Borozzi, defenders Tom Galati and Gene Mishalow, backup goalie Bob Stetler and forwards Sonny Askew and Peter Silvester, the leading scorer in exhibition with four goals, are the other new Washington players. Of the current 21 players (the roster must be cut to 17 by Sunday), only eight played with the Dips in 1976.

Spavin thinks that may be a bonus for the Dips.

"A lot of the guys will be out to make such a good showing we may not miss the players who aren't here," said Spavin. "Besides, every club in te league may be experiencing the same problem with English clubs.

"We're not going to panic if we lose a game or two. We have a long season and no one will go through it undefeated. We'll know by 4:15 or whenever the game is over Sunday just how far we'll have to go."