“The corner [outfield] guys definitely have more freedom to play the hitter and not worry about giving away too much,” Washington right fielder Jayson Werth, above, noted of having Denard Span in center and moving Bryce Harper to left. (Alex Brandon/Associated Press)

Defense hides in plain sight. Baseball’s prettiest, trickiest but most dependable element is also its most mysterious. Everybody wants it, but nobody knows exactly what it’s worth in runs, wins or dollars or how much to sacrifice to add more of it. But the Nationals are about to get an education.

The Nationals traded away a slugger, Michael Morse, who has already hit nine homers in spring training and four more in just three games of the regular season, both totals that lead MLB. Morse was a poor left fielder, perhaps an adequate first baseman and a fine slugger. The Nats went in the diametrically opposite direction, keeping gold-glover Adam LaRoche at first base, adding a swift center fielder in Denard Span and moving a decent center fielder, Bryce Harper, to left field, where he should excel. It’s like a controlled lab experiment. Now, we get to see how it works out.

The Miami Marlins think it’s working entirely too well. They know they’re bad. But they probably didn’t expect to come to Washington for three games, lose them all and score only one run on the entire trip.

In the first inning on opening day, Ryan Zimmerman saved a run with a diving stop and throw from third base that LaRoche dug out at first base. After that, the leather never stopped slapping the poor Fish in the gills every time they tried to compete. On the last out of the Nats’ third straight win, Harper made a running over-the-shoulder catch.

During the sweep, Jayson Werth turned a triple into a double and a double into a single on hits down the right-field line. Span ran precise routes in center to make cruising catches in the gaps. Danny Espinosa and Ian Desmond turned double plays. Jordan Zimmermann made two quick off-the-mound fielding gems, including a force at third base in his 6-1 win on Thursday afternoon. And Kurt Suzuki threw out Juan Pierre stealing.

The Washington Post’s Mike Wise offers his extra points about Bryce Harper and his future professional baseball career. (Post Sports Live)

In three games, the Nats had one misplay but perhaps eight defensive plays worthy of a star, including a double-rundown double play that went into the scorebooks 7-2-3-4-2. Seldom seen. “Executed perfectly,” said Manager Davey Johnson.

“As a pitcher, you’ve got an unbelievable infield behind you — all four are gold-glove caliber. You’ve got speed all over the outfield. Dare the batter to put it in play,” said Zimmermann, who struck out just one.

Nats GM Mike Rizzo always planned for the team he sees now. “Twenty-seven outs — and no more — that’s our goal,” he said. “You can’t afford to give good teams extra outs or they’ll kill you. We want pitching, defense, athleticism and speed wherever we can get it.

“Michael [Morse] is in the perfect league for him,” added Rizzo. “We’re more of a National League type club — a layered [left-right] lineup, more on-base percentage. And there’s a dramatic difference in our outfield. We took a pretty good center fielder and put him in left. Because Span takes perfect routes to the balls in the gaps, our corner outfielders can shade a little more toward the corners, even get to more balls in foul territory.”

The Nats total outfield coverage is already radically different. Last season, Harper had to play deep because he was a novice not used to going back on balls over his head. Span has no such fear and gets to more balls in front of him.

Werth points out another difference. “Last year, we had Mikey, so we had to protect his [lack of] speed a little bit. The corner guys definitely have more freedom to play the hitter and not worry about giving away too much anywhere.”

Of Span’s sprinting catch in front of the right field scoreboard on Wednesday night, Werth said, “He made it easy. Not saying Bryce wouldn’t have made that play. But it might have been one of these miraculous plays that he makes, where you’re like, ‘Oh my God! What an unbelievable play!’ Denard, like, jogs the last five steps, no problem. That’s where TV, it’s kind of like hockey in a sense. It doesn’t do the outfielders justice.”

Time will tell if the Nats pay a price for that smooth defense. Without one of their big thumpers from 2011-’12 in Morse, will they actually produce as many runs (731)? Starting Friday, the Nats play 17 games against the first-rate Reds, Braves, Cards in the next four weeks. Span, on base in half of his 12 at-bats, is doing exactly what’s asked, beating out a bunt and forcing a throwing error Thursday.

What’s already clear after just one series is that excellent defense can smother the life out of bad teams. Bad teams know they stink. When they see hits stolen from them, rallies squashed, extra bases rescinded in an instant and base runners thrown out at home, they wonder why they bothered to come to the park. The Marlins left flat as flounders.

“We’ve had trouble with the Marlins no matter what — every year, whoever they put out there,” said Johnson. “Good to spank ’em this time.”

Stifling weak teams is always essential to contenders. But it’s seldom mattered more than it will to the Nats this year because they play 72 games against teams that are no better than 66-to-1 to win the World Series. The Nats not only play the decimated Marlins and the Mets 19 times each, they also play 34 games against the Rockies, Twins, Padres, Cubs, Pirates and Indians.

The jury will be out for six months on the Nats’ subtle switch to better defense and a leadoff man who’ll probably count his homers on the fingers of one hand. But one thing is certain: defense is baseball’s eye candy. Night after night, this will be an aesthetically exciting team to watch, one that seldom hands away games and often defends like a band of thieves.

How good are their gloves? Well, who is the Nats worst defender? Having a hard time choosing? So is Werth. “That’s really hard,” he said after his three-run, 425-foot home run iced Thursday’s win.

“I take a lot of pride in my defense,” said Werth, who’s considered a “plus” defender. “But most people would probably say it’s me.

“That’s quite all right,” he said grinning. “If I’m the worst, it’s a good problem to have.”

For previous Thomas Boswell columns, visit washingtonpost.com/