The way the Boston Red Sox are holding firm in first place, the New York Yankees are fussin' and feudin' in customary fashion and the Baltimore Orioles are streaking, few have noticed that there is a fourth contender in the American Leaque East these days.

Keeping pace with the "Big Three" are the Milwaukee Brewers, who are off to their best start in history with eight straight victories, 11 of their last 12 and a 33-26 won-lost record.

Before the season began, my thinking with this club could play 500, possibly better," rookie Milwaukee Manager George Bamberger said Wednesday night after the Brewers completed a 7-5, 5-0 doubleheader sweep of the Toronto Blue Jays. "Nobody said we'd win the pennant. If we were in the other division we would win the pennant, but the three best clubs in base-ball happen to be in the same division - ours. Red Sox 9, A's O

Carl Yastrzemski hit a three-run homer, Jim Rice knocked in three runs with his 20th homer and a single and Luis Tiant spaced four hits for Boston's 31st win in 41 games. Tiant, 6-0, struck out six and walked none. The Red Sox are 25-4 at home. Yankees 11, Mariners 9

Paul Blair hit reliever Enrique Romo's second pitch for a three-run homer in the 10th inning. Seattle, which earlier got a grand-slam homer from Craig Reynolds, went ahead, 9-7, in the top of the 10th on a solo homer by Leon Roberts and a sacrifice fly by Ruppert Jones. Sparky Lyle hurled the final five innings to get the win. White Sox 4, Rangers 1

Still another streaking club, Chicago, made it 16 wins in 18 games as Ron Schueler and Jim Milloughby pitched a three-hitter. Alan Bannister and Chet Lemon drove in two runs apiece for the Chisox, who have made up 10 games in 18 days, moving to within 2 1/2 of first place in the AL West. Royals 7, Tigers 1

Amos Otis capped a four-run third inning with a two-run homer and Paul Splittoroff, 8-5, went all the way on a four-hitter. Fred Patek, Hal McRae and George Brett all drove in runs with sacrifice flies. Detroit has dropped four of five. Twins 8, Indians 2

Dan Ford belted a two-run homer and rookie Roger Erickson scattered 10 hits for his seventh victory. Ford's eight homer capped a three-run fourth inning and David Clyle took his first loss of the season. Roy Smalley had two RBI for Minnesotsa. Dogers 5, Mets 3

Bill Russell's two-run, tie-breaking double in the seventh triggered Los Angeles over New York Steve Gravey belted two home runs off loser Jerry Kosman, his second homer tying the game in the sixth inning. Pirates 6, Astros 4

Dave Parker slammed a three-run homer and reliever Ed Whitson gained his first victory of the season as Pittsburg rallied from a four-run deficit to beat Houston. Braves 7, Cardinals 1

Jeff Burroughs and Dale Murphy belted home runs to power Atlanta over St. Louis. Adrain Devine, making only his second start of the year, stopped the Cardinals on five hits before giving way to reliever Rick Camp in the eighth inning. Padres 6-1, Expos 2-0

Gene Tenace knocked in two runs and Dave Winfield hit a solo homer to pace San Diego's first-game victory over Montreal. Eric Rasmussen pitched 6 1/3 innings to gain the victory while John D'Acquisto finished up for his third save of the year.

The Padres completed a sweep in the nightcap behind Gaylord Perry's four-hitter and Winfield's RBI single.