If statistics mean anything, tonight's 8 o'clock soccer game at RFK Stadium between the Washington Diplomats and the Vancouver Whitecaps will be a long one for the forwards.

At one end of the field will be Vancouver goalkeeper Phil Parkes, the leading goalie in the North American Soccer League last year by a wide margin and the leader again this season with a 1.00 goals-against average.

At the other end will be Washington's Bill Irwin, who is keeping Parkes from making a runaway of the goalkeeping race this season. Irwin is second in the league with a 1.15 average.

But when Irwin and Parkes take the field neither man will be thinking about the other. "I'll have enough on my mind just worrying about their forwards without worrying about what he's doing."

Parkes feels the same way. "I know he's an excellent keeper but as far as I'm concerned what makes that significant is that it may be tougher for us to win because he makes a big save."

Both Washington 15-7, 133 points, and Vancouver come into the game off impressive wins, the Dips having beaten Seattle, 3-1, Sunday while the Whitecaps were shocking the Cosmos, 4-2, in Giants Stadium.

Vancouver 14-8 for 124 points, is one of the NASL's best franchises and also one of its best-kept secrets. Last season led by Parkes' 10 shutouts, the club had a 24-6 record, the same as the Cosmos. The team is averaging more than 20,000 fans at home.

Irwin, who has watched Parkes play several times, attributes much of his success to his experiences. "He's been doing it for so long he always seems to be in the right place." Irwin said. "He has played in the English League first division and that's about the best league in the world. You won't catch him out of position."

Parkes, 32, turned pro at age 15 and played in the English League for 14 years before coming to Vancouver on loan in 1977. He liked it there so much he returned permanently in 1978.

"Vancouver's a lovely city, I'm glad to have my family living there," he said. "My son (age 7, also a goalie) really likes it and my baby was born there.

"The league's gotten better every year. There are some teams now which could compete in the first division."

Irwin, 26, never played in the first division, but Parkes thinks he could handle himself well there. "He uses his size (6-foot-3) very well," Parkes said. "He's very rangy, gets to most crossing passes before the forwards do."

"It's a very important game for us," Irwin said. "We know we have to win at home because we have a road trip coming up and we want to stay as close to the Cosmos as we can. Vancouver's very tough."

And one of the main reasons Vancouver is so tough is the day-in-day-out consistency of Parkes. "I enjoy the job," Parkes said. "I'm 32 now. If I didn't enjoy it, I'd stop doing it."

That would greatly please NASL forwards.

Kevin Hector is Vancouver's leading scorer with 15 goals and six assists for 36 points . . . Dips' leading scorer Alan Green suffered a foot contusion Sunday and is doubtful for tonight. If he cannot play, Ken Mokgojoa probably will be his replacement . . . The Cosmos will play at Fort Lauderdale tonight; they lead the Dips by 13 points . . . Dipomat left back Tommy O'Hara will be back in the lineup tonight.