In case you've been away for about a decade, baseball has changed. Fundamentally. It's guys like Tim Raines who have done it.

Monday night here against Los Angeles, the Montreal rookie, who has stolen 26 bases in 24 games this season, broke from first base as Rodney Scott hit a one-hop single to the right fielder. Running all the way on the two-out, 3-2 pitch, Raines never hesitated. He was going to score from first base on this clean single directly at a charging outfielder. Dodger Rick Monday knew what Raines had cooking and, in his frustations, bobbled the ball fora split second before gunning his throw to the plate.

The only difference it made was that Raines scored standing up instead of, perhaps, having to slide. The 21-year-old rocket man was in the on-deck circle slapping hands before the ball was warm in the Dodger catcher's glove.

The combination of quick, artifical turf, which effectively shortens the distance between bases by a full running stride for a speedster, and the influx of new players with sprinters' speed, have transformed the basic dimensions -- the angles and timings and nuances and strategies -- of baseball.

"If Raines can get on base 250 times a season, and it looks like maybe he will, then I think he has a good chance to break all the stolen-base records in the book," said John McHale, president of the Expos. "Yes, I mean Lou Brock's 116 in a season."

Plenty of folks in Canada think Raines will do it this year.

In any other year except the one when Fernando Valenzuela of the Dodgers is making headlines, Raines would be the story of the baseball spring. Last season, he was the minor leagues' player of the year, batting .354 at Denver, scoring 105 runs and stealing 77 bases. Great, you say, but hardly earthshaking. Well, he did it in 108 games -- two-thirds of a season.

The Expos were so certain that Raines had the mark of greatness that they did not even attempt to sign temperamental Ron LeFlore when he became a free agent last fall, banking on Raines' ability to make the elementary transition from a hard defensive position (second base) to an easier one (left field).

All winter, Montrealers, who loved LeFlore for his 97 steals and had no idea what baseball people were talking about when they gnashed their teeth over his defense and attitude, agonized over the decision to opt for Raines, whose only big-league experience was a disastrous one -- one for 20 last summer.

So far, he has been better than LeFlore in every area.

After 24 games, Raines not only has 26 steals in 27 attempts (32 for 33 in his carrer), but is hittingh .359. Thanks to 17 walks, his on-base percentage is .482, by far the best in the National League.

In a four-game series last weekend against Los Angeles, he put on a terrifying display of his total abilities. On Friday, he played second base in an emergency, stole three bases (second and third on consecutive pitches), then ended the game in the 13th inning with the first home run of his major league career.

On Saturday and Sunday, he infuriated the Dodgers with four cheap hits -- on bloops, chinks, chops and dribblers. In addition, he stole another base and make a gymnastic, sliding catch in left. And, on Monday, his first-to-home dash on a single proved to be the last and winning run in a 4-3 Expo victory.

Raines' lasting contribution to basebal may be that he is the only base runner, at least thus far in his career, who runs the bases with utter contempt for the opposition. If the base in front of him is vacant, he steals it. Usually, on the first available pitch.

When Raines gets on, it's as though the groundskeepers accidentally put the bases only 80 feet apart and he's the only one who's found out yet, so he's in a hurry to do the maximum amount of theiving in the minimum amount of time before anybody gets wise.

It helps that Raines' particular gift of speed seems perfectly suited to the 90-foot distance. "By my first full stride, I'm at full speed," he says. "In high school, I ran the 40-yard dash in 4.3 seconds, but I'm faster now."

"In his (healthy) prime, " Michkey Mantle got down to first base in 3.9 seconds batting right-handed and 3.75 to 3.8 seconds batting left-handed," says Expo Manager Dick Williams. "If a right-hander can get to first in 4.2 seconds, you say he has decent speed.

"Well, the other day, we clocked Raines to first in 3.57 seconds from the right side. If that's not the record, I don't know what is. Of course, left-handed he's in the 3.4s."

Usually, sprinters are known for their arrogance. Adding to the possiblities that Raines might be vain is a high school football career that included a game when he gained 225 yards and scored four touchdowns in 10 carries for Seminole High of Sanford, Fla. At 5-8, he can also dunk a baseketball.

However, Raines' dominent characteristic is genuine modesty. "I don't like to be talked about a lot," he says softly. "Keep a low profile, ya know. I think about that guy (Ed) Miller in Atlanta who came up last spring (after stealing 91 bases in '79) and said he'd steal 100 bases as a rookie. Next you knew, he was back in AAA, hitting about nothin' (.209). "I don't want to be like that. I'll take it day to day.

"I want the guys on the team to like me. I kid around a lot, but if I get four hits, I don't go around saying, 'Oh, yeah, I'm baaaad.'"

Williams thanks the fates every day that Raines, not Leflore, is hie leadoff man. "Tim is a good, intelligent, determined young man," says Williams. "That's very refreshing around here. Already, Raines is much better dfefensively than LeFlore . . . and he gets to the park on time."

To the casual eye, Raines' skills seem obvious. He has a good sense to use his short height as an edge to get walks. Although he has the muscles for extra-base power, he's canny enough to be a contact slap hitter who can beat out a disgusting assortment of pathetic taps and nubbers. Also, he's learning to bunt.

"Tim isn't the first guy to come along with sprinter's speed. I'm not at all sure that he's the fastest runner in the game," says reliever Woodie Fryman. "But he also has good baseball instincts and he's a student of base stealing. The league thinks it's learning him, but Raines is learning them, too."

Neither Lou Brock nor Maury Wills had world-class speed; they were fast, but not blinding. First of all, they were baseball players, pupils of nunance and the split-second jump.

Raines is a blur with brains.

Perhaps one play exemplifies what Raines brings to the game. Last July 2 in Denver, playing before the biggest crowd in minor-league history (more than 58,000), Raines hit a liner over the center fielder's head that hit the 420-foot sign on one high hop.

"My foot hit second base as the ball was coming down off the wall to the fielder," recalls Raines with a tiny smile that intimates that, if you were there, maybe you'd understand just how close to impossible that is. "As I crossed home plate (with an inside-the-park-homer), I looked over my shoulder and the relay man had just caught the ball."

Let's get this straight, Tim. Line drive off the center field wall. Comes right backl to the fielder. No bad hops. Nobody falls down. Nobody bobbles the ball. And you cross the plate standing up while the ball is still 200 feet away from home.

"Yes."

That's impossible.

"That's what they said," he said with a laugh, once more right as Raines.