When the Seattle Sounders take the field at 2:30 p.m. today in RFK Stadium to face the Washington diplomats, their best-known player will not be in uniform. He will be 3,000 miles away in Seattle, listening to the game on radio.

Jim McAlister is not injured. He has been healthy all season. Yet, his last appearance in uniform was June 13. At that point he and Seattle Coach Jim Gabriel sat down and agreed that McAlister should make a vacation.

"I had lost my enthusiasm for the game," McAlister said this week. "I really didn't care if I played or didn't play. I had stopped caring."

To American soccer fans, the name of Jim McAlister is magic. He is the personification of what they hope American soccer will become.

In 1977, at age 20 McAlister burst upon the North American Soccer League. He led the Sounders into the Soccer Bowl and quickly became known as one of the league's toughest and smartest defenders. His rookie-of-year award was virtually automatic.

Then, in the Soccer Bowl against the Cosmos, McAlister had the honor at game's end (a 2-1 Cosmos victory) of being presented with Pele's jersey by the great man himself.

It was Pele's last NASL game and many saw his presentation of the jersey to McAlister as symbollic - the torch being passed.

"The thing with the jersey plus the kind of season Jim had as a rookie put unbelievable pressure on him," Gabriel said. "Everyone, the media, the fans, his family, myself, other players and Jim himself, were expecting so much. No one meant to put pressure on him, but they did.

"It's easy to see why people wanted him to succeed so badly. Jim is the All-American boy. He's fresh, keen and aggressive. He's just had some growing up to do. And he's had to do it with everyone watching."

McAlister's play tailed off somewhat in 1978 and deteriorated further the first 12 games of this season.

"I think every player reaches a point in his career where for one reason or another it just isn't there any more," McAlister said. "I guess I reached it earlier than some others.

"I had to decide where I'm at in my career right now, decide if I wanted to stay in Seattle or move on. I've done a lot of thinking the last few weeks."

McAlsiter also did some traveling, to New Jersey to talk to the Cosmos about a possible move. But he didn't like what he saw and returned to Seattle to work himself back into shape.

"I think I've got my enthusiasm back now," McAlister said. "The longer I've been away, the more I've missed it. I really want to get back in the lineup now. I feel like I'm ready to play again."

The Sounders have been playing well on their current four-game road trip, winning, 2-1, against the Cosmos at the tmeadowlands Wednesday to raise their record to 10-11, good for third place in the National Conference West. The Dips are 14-7 for 124 points, second to the Cosmos in the National Conference East.

"The team's been playing better together as a unit lately," McAlister said. "You can see things starting to jell. I know I have to keep working hard and wait my turn to get back in the lineup. Meadowlands the call comes, I hope ti'll be ready. I think I've learned a lot from what I've been through the last two seasons.

"You have to learn to ignore publicity. You can't let it go to your head. You have to keep working at the game and not worry about people talking about symbols or anything like that."

McAlister says he is ready to play now. And Gabriel says when Mc alister tells him he is ready to play, there is a spot waiting in the lineup for him.

"When the prodigal son returns you welcome him home," Gabriel said. "You don't leave him standing on the doorstep."

Left back Tommy O'Hara of the Diplomats suffered a foot injury in practice Friday and is questionable for today.Ane Mihailovich will take his place if O'Hara cannot play.... Mike Dillon returns at one center back spot but Don Droege is still out.