The Minnesota Twins almost won a game without Mike Marshall tonight. If they had, it would have been a dreadfully dull way for the Baltimore Orioles to end their 18-day stay atop the American League East.

As it was, Baltimore loyalists in the crowd of 11,036 were treated to a lone hurrah in the bottom of the ninth, when Ken Singleton and Gary Roenicke had opportunities to hit a game-tying home run. However, Singleton grounded to reliever Marshall, Roenicke struck out, the Twins were 3-1 winners and the Orioles were four percentage points behind the Boston Red Sox.

The boredom was supplied by Minnesota right-hander Paul Hartzell, who did not permit an Orioles past first base until the ninth inning. The Lehigh grad then threw high fast ones to Al Bumbry, whose blooper was caught by diving Bombo Rivera in left; to pinch hitter Pat Kelly, who bounced a double over the fence in right, and to Eddie Murray, who drilled a single to center.

Enter Marshall, a loser the night before.

This time, he recorded his 12th save to go with eight victories, and that accounts for the major part of the Twins' 29 successes this year. While Oriole fans were thinking home run, Marshall was thinking out. He has given up one homer this season, only three last year.

"The hitters know if they go at me with a big swing, I'm going to get them out," Marshall said. "I throw soft and I throw hard, change the pace all the time. I try to keep the ball on the ground, take the sting out of the bat and at the end of the season, we should be happy."

Although the shutout disappeared with Singleton's grounder, Hartzell was happy. He yielded five hits, walked none to extend his walkless streak to 26 innings, went to three balls on only one batter and beat the Orioles for the third straight time.

The 6-foot-5 hurler, acquired by Minnesota in the Rod Carew deal, benefited from some excellent defensive play by Rivera, three outstanding catches, and third baseman John Castino, flagging down Doug DeCinces' eighth-inning grounder reaching backhanded behind the bag.

Oriole third baseman DeCinces, making his first appearance since he tore a back muscle April 26, was less successful on defense, along with second baseman Rich Dauer, and their misplays were the difference on the scoreboard.

Steve Stone, losing his fourth straight decision, walked Castino on four pitches to open the Minnesota third. Rivera sacrificed and Hosken Powell bounced one off DeCinces into left field. It was eminently playable, but it took a "Baltimmore hop," and excusable bounce that exists only in the minds of Baltimore scorers.

Butch Wynegar poked a bit past first baseman Murray's glove for the first run and Roy Smalley, the American League batting leader, blasted one into right for a 2-0 lead.

Minnesota made it 3-0 against Scott McGregor in the eighth.

Powell hit a leadoff pop fly down the right-field line and Dauer, crossing the line, suddenly reached back in vain as the ball fell fair for a double. Wynegar sacrificed and Smalley, permitted to bat with first base open, despite his .384 average, whacked a sacrifice fly to deep center.

Hartzell has only 24 career victories, which makes his 1.30 lifetime earned-run average against Baltimore a mystery. It is partly explained, however, by the fact that he pitched for Leone's semipro team here during a Lehigh summer.

"I pitched here when I was 19 years old and I've always enjoyed this town," Hartzell said. "I like this field. I think it's the best in the league. I like the lights and I'm going to ask them what grass they use so I can plant some at home.

"You can concentrate more when you enjoy being out there in pleasant surroundings. Concentration is the secret to control. If you keep the ball over the plate and keep it low, with these guys behind you, you'll win a lot of games. I've thrown as hard on other occasions, but that's the best location yet."

"He threw 90 percent fast balls - that's his out pitch," said catcher Wynegar. "He had the best sinker I've seen him throw. And he's usually in control but tonight he was exceptional. He has to stay down and he did for eight innings, until he got the ball up to the first three hitters in the ninth."

And gave the fans a chance to dream up a dramatic ending.

Earlier in the day, the Orioles sent outfielder Larry Harlow to the California Angels in exchange for minor leaguer Floyd Rayford and cash. Rayford, an infielder, has been playing with Salt Lake City in the Pacific Coast League, and will remain there on Oriole option.