hey are three strangers in a strange land, playing a hoked-up game and having an increasingly good time at it.

The happiest news was on the sign on the Civic Center that said, "Tonight, Cleveland, Sold Out."

In the middle of the week between Christmas and New Year's, the Baltimore Blast of the Major Indoor Soccer League was about to enjoy the first weekday sellout in its three-year history and its fifth full house in seven home games this season.

In the Blast locker room, thick with the odor of liniment, three athletic refugees prepared for another night of rough body contact on plastic grass.

Two years ago, they were Diplomats, cogs in the Washington entry in the dignified North American Soccer League. But the Diplomats rarely drew throngs and, in the end, the franchise folded, leaving Petar Baralic, Davey Bradford and Heinz Wirtz jobless immigrants.

One by one, they found the Blast. In time, they honed their skill at "American soccer," as to a man they describe the irreverent indoor game. Now they are stalwarts of a hot sports franchise.

These are classy soccer players. Purists might say putting them to work on a field smaller than a hockey rink, having them bang the ball off the sideboards, pulling them out for substitutes every two minutes and spurring the whole show on with shrieks over the P.A. system is like playing Bach on a kazoo. Tacky.

But in America, as prime-time TV suggests, tackiness is no impediment to commercial success.

So at 7:35 p.m. Wednesday, with the packed house (the third sellout in the last four games) rocking and reeling to about 7,000 watts of the pop song, "You Can Do Magic," an immense orange-and-black soccer ball descended from the darkened ceiling of the old arena, fireworks split the ball in half and Baralic, Bradford, Wirtz and the rest of the Baltimore Blast raced out to the wild cheers of 11,233 admirers. They went on to a 5-4 victory over the first-place Cleveland Force.

Bradford, a tiny Briton with Lord Fauntleroy hair down past his shoulders, said of the Blast fans, who were on their feet and screaming at the end, "They remind me of Liverpool."

But he believes the Baltimoreans who pay $3 to $8 for Blast-ing rights actually go a notch beyond soccer-wild Europeans. "I've seen good fans," he said, "but these beat the lot. They're mad."

Bradford, like his fellow Diplomats' expatriates, is hooked on his new life in the land of instant gratification and growing more tolerant of his new game.

"I couldn't go home now," he said. "In England, if I want to go out and get a bite at 11 at night, I can't. Everything's shut, isn't it? Here, everything's convenient. I can eat when I want. You drive everywhere. You can park your car right outside the grocery store; they have the money machines at the bank."

He admits to missing some of the subtlety of the game he grew up with. "The way I was brought up outdoors is the game, so I'd love to play it again. But it just doesn't happen in this country." And despite the loss, said Bradford, "I couldn't go back."

Nor could the burly Baralic, a native of Yugoslavia who leads the Blast this year in scoring. Says he, "I feel very very nice in this city. I'm not a man who likes to change too much."

For Wirtz, who had a hard time adjusting to indoor soccer, but feels he's finally over the hump, the game remains second-best, "but I have to think as a professional, and here in the U.S. indoor is the only way."

None of the three has relinquished his Washington ties. Baralic lives in Alexandria and Wirtz and Bradford both live in Greenbelt. They just never got around to moving.

At another time in their careers, they would have avoided the city they played in. Said Wirtz, a handsome West German, "When I played in Dusseldorf, I didn't like to go out in the city at night. If I went out, I would go to Cologne where I wasn't known. Almost every player did that."

The reason? "In Germany, people bothered you and not in a friendly way. They think they know everything because they played the game themselves, and they would criticize, especially when they were drunk a little."

In Baltimore, there is no such problem, said Wirtz. "They are beginning to recognize us, and I rather like it," because the comments are mostly in praise, he said.

Watching a Blast game provides something like a soccer primer. The players are "very clever," commented one astute observer watching his third game.

Indeed, the things these veteran soccer stars can do with their feet and heads are intriguingly complicated. From the distance of the stands at a huge outdoor field, much of that skill would go unnoticed by unsophisticated spectators. But when Baralic fakes and drives around his man from the blue line of an ice hockey rink, every hitch and lunge is in plain sight. There's no mystery to a good pass at the goal mouth; everyone in the arena sees how it works, even down to the look of surprise on the face of the recipient.

And in indoor soccer there's a good deal of banging and bumping to keep the action-hungry American fan satisfied.

This suits Baralic, the former captain of the Diplomats. "I don't pay much attention to the danger because I am strong guy," he said with a smile. Wirtz, more of a finesse player, has had to lift weights to build himself up for the stresses of contact.

Bradford, who stands 5 feet 5, runs hard and tries to stay out of trouble.

Wednesday against the Force, time was called at least three times as trainers raced out to administer to injured players, including Wirtz, who survived a vicious head-clanking with Cleveland star Kai Haskiivi.

Bradford, called "the Mighty Atom," was getting his rug burns patched up after the Force game when he was asked if he always played so hard.

"Sure. It's fun, you know. But I could do without these," he added, grimacing at his wounds. "Pity they couldn't have put a roof over that nice grass at RFK."