Fernando Valenzuela may not be able to speak much English, but he speaks eloquent pitcher. With a fast ball on the fists, he is pithy. With a sweeping curve ball, he is poetic. And, above all, with a screwball of varying speeds, he is the most fluent of southpaws.

Again today, the 20-year-old Los Angeles rookie, who looks like a tub of butter but hurls like a barrel of gold, was brilliant in pitching the Dodgers to victory, this time 6-1 over the Montreal Expos in 10 innings.

Actually, by Valenzuela's exalted standards, this was a lousy performance.

He actually gave up a run. One run.

And, for the first time in the big leagues, he needed relief help as Steve Howe got the save, working the 10th after the Dodgers had rallied for five runs in their half of the extra inning to make Valenzuela the first six-game winner in the majors this season.

A cheap Astro-Turf hit -- a homely grounder by Chris Speier past immovable Los Angeles third baseman Ron Cey with two out in the eighth inning -- broke Valenzuela's latest streak of scoreless innings at 36. The unfortunate Mexican left-hander saw his ERA for the season skyrocket from 0.20 to 0.33; in the 71 2/3 innings of his major league career (17 2/3 innings at the tail end of last season), Valenzuela has allowed two earned runs.

If the truth be told, this may actually have been Valenzuela's best showing. Against an intimidating team of right-handed power hitters, Valenzuela was completely poised, always in control and fearless as he changed speeds and made hitters like Andre Dawson, Gary Carter and Larry Parrish (0 for 15 among them) look as though they were the ones who were rookies.

After the leadoff hitter for Montreal, Tim Raines, beat out an infield hit in the first inning, Valenzuela, who is now 8-0 in his short career, retired the next 21 Expos in a row. In all, Valenzuela worked nine innings, gave up five hits (two of them dribblers and one a seeing-eye grounder), while walking no one and striking out seven men.

The 5-foot-11, 190-pounder got the win when the man who pinch hit for him in 10th, Reggie Smith, drove in the go-ahead Dodger run with an RBI single that broke up a 1-1 pitcher's duel and made a loser of gallant 22-year-old Bill Gullickson.

With one out in the 10th, Gullickson (1-2) walked Mike Scioscia. Bill Russell singled to put runners on first and second. Smith singled in one run and Dave Lopes followed with a single to load the bases. Ken Landreaux singled home Russell before Dusty Baker drove in another with a sacrifice fly. Steve Garvey completed the scoring with a two-run single and was tagged out trying for a double.

In over a century of brilliant rookies and splendid phenoms, there has never -- underline that emphatic word "never" -- been a pitcher who has announced himself to major league baseball with such excellence as Fernando Valenzuela.

You can talk about 'em all -- Ty Cobb seeing Walter Johnson for the first time and saying -- "You can't hit what you can't see" -- but no one has put together the kind of introductory numbers that Valenzuela has amassed. In 54 innings over six starts in '81, Valenzuela has allowed 33 hits and 11 walks while striking out 50. Counting his 10 shutout relief appearances of 1980, Valenzuela, over those 71 2/3 innings, has allowed just 57 base runners while fanning 66 men and somehow creating the psychedelic career ERA of 0.25.

The reaction of both the Dodgers and the Expos to Valenzuela's stellar late afternoon in the Olympic Stadium shadows was typical of his season so far.

"Just like always . . . great," said Dodger Manager Tommy Lasorda.

"How'd he get so old so fast?" asked L.A. second baseman Dave Lopes. "He pitches like some 35-year-old guy who hurt his arm 10 years ago and had to learn all the tricks."

"I wanna see him again," grumbled Expo all-star catcher Gary Carter. "He's obviously very good, but you measure greatness over years, not weeks. What do you do against him after you've seen him time and again? That's the question."

Yet in his more casual comments, Carter showed his real opinion. "He has the screwball and the control that Randy Jones had when he won the Cy Young Award," said Carter. "But he also has a fast ball that's good enough to spot anytime he wants to. Also, he's got a good curve ball."

So, Valenzuela's like a Cy Young winner, except a lot better. At least for now.

Some pitchers have stuff. Some have an assortment of pitches that complement each other, each looking like the others until the last dastardly second. Some have masterly control, not only for strikes but to precise edges of the plate. And some pitchers exude a charismatic sense of certainty that they will win.

No matter what happens to his arm, his psyche or his stomach in the future, Valenzuela has them all in the spring of 1981.

As the inning began, the crowd of 46,405 was in a buzz over a wonderful potential controversy. The first Expo hitter of the game, Raines (20 steals in 19 games), had beaten out a one-hop chop to Cey which, instant replays showed, should have been an out by a clear foot. When Valenzuela then set down the next 21 batters, not allowing a Montrealer to get a ball out of the infield until the sixth, it became obvious that, except for ump Paul Pryor's forgivable mistake in the first, he would have entered the eighth inning with a perfect game.

Pryor got off the hook as Warren Cromartie opened the eighth with a clear single to center off perhaps the only really poor pitch Valenzuela threw all day, a high, hanging curve.

So Speier lived to swing again and nudged a big curve on the ground to third. Any third baseman not hugging the line, or, perhaps, any third baseman except Cey, might have flagged the ball, or at the least kept it in the infield. However, the range of the left side of the infield is the Dodgers' most glaring weakness. Valenzuela's shutout was lost.

Lasorda ended the press party, saying, "Gentlemen, let's hurry up. This is a very tired young man."

Valenzuela, whom many suspect has learned some English as quickly as he has learned all of pitching, gave a sly, private smile.

He didn't look tired. Valenzuela ran his finger across his forehead and looked at it. It was dry. He hadn't even broken a sweat.