MOSCOW (AP) _ The third baseman reached for the line shot after it already whistled over his head. The left fielder got to the ball once it stopped rolling, and the center fielder dropped his relay throw.

After that opening play Thursday, three pitches after the umpire called 'Pley bol 3/8'' it was all downhill for the Soviet national baseball team.

Nicaragua's leadoff hitter was home. His team was on its way to trouncing Soviet third baseman Boris Budarin, left fielder Viktor Zaitsev, center fielder Dmitri Shlyapnikov and teammates in their first appearance in Moscow.

The two teams packed it in after four innings on a gray, drizzly 50-degree afternoon, but not until the Nicaraguan national team had scored 17 runs - or was it 18, or 16? There were different counts and no official scorer.

The Soviets managed to get a runner to third base in the bottom of the fourth when Nicaragua's right fielder slipped on wet grass tracking a high flyball.

Baseball will become an Olympic sport in the 1990s, and the Soviet Union is six months into a program it hopes will allow it to compete with European national teams.

Even though some Soviet writers have suggested that baseball actually is rooted in the ancient Russian game of lapta, the country has no baseball tradition and almost everyone is starting from scratch.

On Thursday, Soviet Coach Alexander Ardatov said his team played poorly, ''just like they played two months ago.'' He was at a loss for reasons, but finally suggested it was the excitement of playing in Moscow for the first time.

Soviet teams had similarly futile games against the Nicaraguan team in Kiev last week, when they lost 22-0 and 30-2.

They have many problems to iron out, and the players and coach can't agree on which is the worst.

Ardatov said batting is hardest to master because there is nothing similar in the sport with which his players, young men skilled in a variety of other games, are familiar.

Maxim Malakhov, a second baseman for the team sponsored by the Moscow Chemistry Institute, says the problem is reacting to the game situation.

''We do all right with throwing, but every time we make mistakes where to throw the ball, how to throw the curve ball or slider,'' said Malakhov, who carries a copy of a Sports Illustrated book on pitching in an inside pocket.

The Soviet players, dressed in red sweatshirts and dark sweatpants, knew what they had to do but reacted more slowly than players steeped in the game since childhood. The Nicaraguans' routine singles became doubles, and doubles became triples or home runs.

Nicaraguan batters sent Alexander Dudkin's pitches flying all around the inside of the quarter-mile track used for the playing field, and over the fence separating it from Moscow's Olympic Village.

But the Soviet players kept their sense of humor, laughing and chatting on the bench, and their confidence that they will be ready for bigger things in the near future.

''I think in three or four years we can play in Europe, against the best teams of Europe,'' said outfielder Andrei Tselekovsky. He sports a Pittsburgh Pirates hat and a glove autographed by pitcher Kent Tekulve sent to him from the United States by Pittsburgh resident Trish Beatty, whom he met in Moscow earlier this summer.

About 100 curious Soviets gathered under their umbrellas at the start of the game, watching casually and listening to a patient explanation in Russian on the public address system. A few others, seemingly oblivious to balls flying around them, jogged around the track.

When Nicaragua's No. 3 hitter sent a pitch sailing over the right-field fence, the announcer instructed viewers that it was the ''most, most, most valuable hit.''

When right fielder Alexei Koshevoi caught a fly ball to end Nicaragua's 11- run first inning, he shouted, ''Urah 3/8 Urah 3/8 Urah 3/8''

He took pains to explain that the Soviet team has been playing baseball for six months while the Nicaraguans have been playing for years.

The audience gradually trickled away, but 13-year-old Seryozha Kommisarov and his two friends, 15-year-old Seryozha and 13-year-old Pavel, lingered to watch for a while.

Seryozha Komisarov said it looked like a good game, and that he would like to try it sometime. Everyone wanted to know what the Nicaraguans' shiny metal bats were made of, and how much they weighed.