BOSTON — If you didn’t know any better, you might mistake the 2007 Los Angeles Angels of Anaheim for a 1980s National League artificial-turf team.

In contrast to most current American League teams, the Angels don’t swing for the fences and wait for the big inning. Instead, like some up-tempo, fast-break basketball team, they run as much as possible and apply pressure on the opponent.

The Angels finished fourth in runs scored, but they did it with aggressiveness on the base paths. Ranked 14th in homers and 9th in slugging percentage in the American League, they were second in stolen bases and led the league in going from first to third.

“We have to keep the pressure on for nine innings,” said manager Mike Scioscia. “That’s how we get into our game.”

And don’t think the Red Sox are unaware.

When the teams open their 2007 best-of-five American League Division Series tonight, the Red Sox must be wary of what the Angels do on the bases. Not only will the Angels steal — four players finished with at least 18 stolen bases — but they’ll also take extra bases whenever possible.

“They try to take [an extra] base on every ball hit to the outfield,” said catcher Jason Varitek. “So we’ve got to back up every base and do the little things [to stop them].”

Since the start of the 2003 season, the Angels have advanced a runner from first to third more than any team in baseball. This year alone, they did it 122 times — a far cry from most other A.L. clubs.

“Taking the extra base,” said speedy rookie outfielder Reggie Willits, “is drilled into you from the day you sign [with the Angels].”

For the Red Sox, that puts a premium on good outfield play. Defensively, the Sox boast two above-average defenders in center (Coco Crisp) and right (J.D. Drew). Left fielder Manny Ramirez can be an adventure in left, but has at least mastered the art of getting the ball back into the infield quickly, limiting opportunities for baserunners.

“You have to be constantly aware of where they are [on the bases],” said a longtime advance scout of the Angels. “If you drop your head, or take an extra second getting to the ball, they’ll take off and make you pay.”

The Sox saw what the Angels’ speed and aggressiveness can do when the Angels took two-of-three from them in Anaheim in early August

“I think that’s the one thing that everybody kept talking about,” said Game One starter Josh Beckett. “It was the fact that they play the game the right way, the way they have to win. [So we] have to play the game right, too. You’ve got to hold baserunners.”

Despite the Angels’ base-stealing capability, the Sox vow not to be obsessed with their baserunners. If pitchers pay too much attention, their focus on the hitter can suffer.

“Sometimes,” said manager Terry Francona, “we don’t feel a stolen base will break our backs, whereas a three-run homer will. Then, there are times when you absolutely need to not only not have a stolen base, but you don’t [even] want the attempt.”

As such, the Sox don’t necessarily insist that their pitchers utilize a slide-step — an adjustment in their delivery out of the stretch that enables them to get the ball to the plate quicker.

“It isn’t so much the slide-step,” said Varitek. “There are other things that you can do — hold the ball a little longer [to prevent big jumps], changing looks. Those things are more important than a slide-step.”

The problem with the slide-step is that, in changing a pitcher’s mechanics, it can also impact the quality of the pitch. Breaking balls, in particular, tend to flatten out with different mechanics.

“Maybe if you’ve thrown three straight balls,” said Varitek, “you don’t want to overcompensate and leave the ball out over the middle of the plate.”

If the Red Sox can’t shut down the Angels’ running game, the Angels themselves are sometimes capable of doing it to themselves.

“They can be too aggressive at times,” said one scout, “and run into some outs. If you’re sound fundamentally, you can take them out of their game.”

Of course, the best strategy is to keep them off-base altogether, a feat more easily accomplished by scoring first and putting them on the defensive.

smcadam@projo.com