Swedish Victory Cuts U.S. Lead in Half : Tennis: Having lost in doubles, American team looks to Agassi and Sampras to clinch Davis Cup semifinal today.

The subject of Davis Cup singles dominated the day here Saturday, even though they didn’t play any.

The action on the court, as it were, found Stefan Edberg and Jonas Bjorkman of Sweden beating Todd Martin and Jonathan Stark of the United States, 6-3, 6-4, 6-4. That took 1 hour 50 minutes, narrowed the United States lead over Sweden to 2-1 in this best-of-five semifinal and attracted 10,353 to the Caesars Palace tennis stadium.

That gathering was 2,068 fewer than the 12,421 sellout of Friday, indicating a fairly high level of sophistication on the part of Las Vegas tennis fans. Any resemblance between the Martin-Stark duo and U.S. Davis Cup doubles teams of the past, as in McEnroe-Fleming, Flach-Seguso or Leach-Pugh, was purely coincidental. Afterward, Martin and Stark announced that they had committed to play as a team all of next season, undoubtedly triggering a wave of fear throughout the ATP tour.

In their defense, Martin and Stark were playing together for only the second time, and they were playing a team that was much more than simply a pair of guys who wandered onto the same side of the net.

Edberg, one of the greatest players ever and certainly one of the best ever at the net, spent a year or so ranked No. 1 in the world in doubles in the mid-1980s, when he was younger and better able to play both. And Bjorkman, whose regular partner, Swede Jan Apell, is out because of a shoulder injury, has spent most of the last two years ranked in the top 10 in doubles.

Even Stark recognized the current hole in the ranks of U.S. doubles teams when he said afterward, in reference to Davis Cups of the future, “I think it’s important that we find somebody.”

The doubles outcome created a number of interesting scenarios for today’s singles wrap-up and the quest for that clinching third point.

The first match will pit Andre Agassi, No. 1 in the world and No. 1-plus in the hearts of his hometown fans here, against Thomas Enqvist, No. 8 in the world and Sweden’s current top player since the gradual decline of an aging Edberg. Tom Gullikson, the U.S. captain, characterized that match as “two power baseliners going at it. A slugfest.”

But if Agassi-Enqvist is Ali-Frazier, then the second match, as it is currently scheduled, is more Tyson-Tiny Tim. Pete Sampras, whose big game begins with 125-m.p.h. serves, continues with confident volleys and also includes an occasional 100-m.p.h. ground stroke and service return, will go against Mats Wilander. Wilander, onetime No. 1 in the world, is now, at age 31, still competitive at No. 50, and foxy and crafty and all those things that give him a chance to win against almost any opponent.

Except probably Sampras. On paper, Sampras-Wilander looks like a bazooka against a BB gun.

As no less an authority than the always-understated Edberg said, “If Enqvist gets hot, he has a chance against anybody in the world. Wilander against Sampras? That’s a little tougher.”

Sweden’s captain, Carl-Axel Hageskog, was even more blunt: “If Sampras is playing 100%, Mats has not a big chance.”

Sampras-Wilander very likely will be a moot point, of course. With a clinching victory by Agassi, played out before an adoring hometown crowd, Sampras and Wilander will be reduced to a best-of-three-set exercise that will make one of those Thursday night exhibitions at the Forum look competitive.

But the what-ifs--as in “what if Agassi doesn’t win?”--created much discussion here. And that discussion centered on how Sweden might be able to sneak in the veteran Edberg, who didn’t play singles Friday because he had a cold but who has since shaken the sniffles, as a substitute for Wilander. The conclusion was that, to do that, the Swedes would have to pull a fast one, something not likely, but also not impossible.

“The only way anybody can substitute after the team is announced is because of an injury,” said Christopher Stokes, marketing director for the sanctioning International Tennis Federation. “A neutral doctor would have to be called, and we would need a medical certificate before we would allow that.”

Stokes could think of only one time when a last-second injury substitution like that had occurred. He recalled a 1987 match, when Kent Carlsson hurt himself warming up for the fourth match against Czechoslovakia, and Mikael Pernfors was called in to play.

Pernfors won the deciding match. For--guess who?--Sweden.

Early Saturday morning, as he pushed his baby in a stroller through Caesars Palace, Wilander’s health looked fine. Nevertheless, there is no way to predict the possible wear and tear of stroller-pushing--or even craps-shooting--on a person’s hamstrings.