The Baltimore Orioles, the only team in the major leagues without a victory, bring their beleaguered act home this afternoon to face, of all teams, the Milwaukee Brewers, the only undefeated team in baseball.

Milwaukee, 5-0, bombarded Baltimore, 11-3, 16-3 and 13-5, in the first three games of the season. The Brewers then whipped the defending world champion New York Yankees two straight. The Orioles, meanwhile, lost two more in Kansas City, giving them an embarrassing 0-5 record.

The Orioles have had weal pitching and even weaker hitting.

Their starting pitcher in today's 2 o'clock home opener will be Dennis Martinez. He has pitched 4 1/3 innings this season and has an earned run average of 16.62.

In their five defeats, the Orioles have been outscored, 49-15, and their only threat at the plate has been Edie Murray.

Murray has two home runs, three RBI and is batting .333. No other Oriole has a home run.

Murray, last year's American League rookie of the year playing mainly as the designated hitter, started this season at third base, then was moved to first base.

What other changes Manager Earl Weaver has in mind aren't known.

"If we keep losing, I'll make lineup changes until we win," he said. "One thing we have to do is get a regular pitching rotation with (Jim) Palmer in it."

Palmer, the Oriole ace who has won 20 or more games in seven of the last eight seasons, remained in Florida an extra week because of a sore shoulder. He is expected to make his first start Saturday.

"It's been a big difference not having Palmer taking three of our first six starts," Weaver said. "Ie he had pitched a couple of good games, we might be going for .500 Friday instead of trying for our first win."

"Five in a row is no big deal," said outfielder Pat Kelly. "We proved we could overcome a rugged start when we lost four of our first five last year. Why panic?"

George Bamberger, the Milwaukee manager who was Baltimore's pitching coach for the previous 10 seasons, expects the Orioles to pick up with Palmer's return and said that Baltimore "is just going through a cold spell."

Bamberger said he will pitcher Lary Sorensen today with a crowd of about 35,000 expected.

"I don't know how long we can keep going, but one thing I do know - they can't take those five wins away from us," he said.

"I'm the first guy to say managing's not this easy. I'm not popping off, we've been lucky to this point."

Brooks Robinson, who won't be in uniform for a Baltimore home opener for the first time in 22 years, will have his No. 5 jersey formally retired in pregame ceremonies.