United States' Gio Gonzalez delivers a pitch during a World Baseball Classic second-round victory over Puerto Rico on Tuesday. (Mike Ehrmann/AP)

Can you prepare for the postseason in the preseason?

Gio Gonzalez and Ross Detwiler are going to find out. If the Washington Nationals are in the playoffs in October, their two southpaws may be raving about all the valuable experience they got by pitching in the pressurized World Baseball Classic and getting tips from U.S. pitching coach Greg Maddux.

Both have been brilliant, combining for nine shutout innings and establishing themselves as the hottest pitchers on Team USA. Both have praised the experience of pitching for their country. That’s what you’d expect of the bubbly Gio as well as the gung-ho Detwiler, who cut short his honeymoon in December, leaving his wife in Hawaii, so he could fly halfway around the world to go on a four-country USO tour to boost the troops.

Neither has ever looked sharper, thrown harder or snapped off better curveballs. They look ready for October. Too bad it’s March.

You knew there had to be a rub. And there is — a scary one. The case for letting them pitch, aside from their country’s call, is strong in both cases. They are in their primes at 27, old enough to take the weight of big games seven months apart, but they hope, still young enough to survive it.

The Washington Post’s Dan Steinberg, LaVar Arrington, Mike Wise and Jonathan Forsythe discuss debate the Nationals’ growing rivalry with the Phillies. (Post Sports Live)

Neither has had arm problems. And both can use more experience under pressure. Gonzalez lost his 21-win poise against St. Louis in the playoffs, walking 11 men in 10 innings. He needs to get back on the horse. Detwiler was stellar in Game 4. Given his big talent but shy manner, this is a chance to rub shoulders with stars and build on that center-stage success.

But there is a “but.” If either of them runs out of gas down the stretch or has arm miseries during the season, everybody, including me, will say the same thing. Was the World Baseball Classic worth the World Series?

The U.S. team has done poorly in previous WBCs. Many stars duck out, fearing injury. Who wants to ramp up the effort so soon after taking off a winter? MLB says fewer players get hurt in the WBC than during spring training. Maybe so, but plenty of pitchers vote with their feet.

Gonzalez and Detwiler didn’t. If America wins its first WBC title, they likely will be cornerstones. Is that a sign of taking unnecessary risks with prize pitchers? You shut down Stephen Strasburg in the playoffs, but you bless sending two-fifths of your rotation to the WBC?

Or is this just another omen that now is The Time of the Nats?

After five elegant, efficient innings to beat Puerto Rico on Tuesday, Gonzalez is now America’s ace, ahead of rusty 2012 Cy Young Award winner R.A. Dickey or Giants postseason star Ryan Vogelsong (3-0, 1.09 ERA).

Detwiler pitched the final four shutout innings Saturday night, thus establishing himself in a difficult vital role. Because of WBC pitch limits, teams need, in essence, a second starting pitcher to bridge the gap to the conventional back-end relievers. Detwiler was so sharp that Manager Joe Torre let him close the game, too, to save U.S. relievers for what proved to be a do-or-die win Sunday. It’s hard duty. Detwiler earned it. But now it’s his.

Detwiler “looked great,” Nationals Manager Davey Johnson crowed to reporters in Florida. “I knew he was going to do good. That was a big shot in the arm for their bullpen.” Then Johnson made one of his quips that so often sound like truth-in-jest. “That’s maybe my other left-hander in the ’pen.”

The tall, skinny Detwiler has not pitched more than 1641 / 3 innings in a year and has excelled in relief. But do the Nats have five quality starters without him? Or maybe Davey is thinking about October already. After all, Tim Lincecum changed last season’s playoffs with five Giant relief outings.

Johnson, who coached the 2008 U.S. Olympic team with Strasburg, thinks having “USA” on your chest can be a unique maturing experience. Representing your country hits some players more deeply than playing for their own teams. And for those such as Gonzalez who have had problems with nerves, it can free them up to play for something beyond themselves.

Gonzalez stands to gain the most. Few all-stars have looked more rattled in back-to-back starts than Gio against the Cards. In his career, he had been 31-1 when his team scored six or more runs. Not in Game 5.

After his win Tuesday, Gonzalez raved about Maddux’s relaxation advice: “Focus on something small. . . . I know from experience in the postseason, I was overwhelmed by all the noise and stuff like that.”

Maddux tip? Think of fielding a routine groundball or going fishing or anything else.

“And I understood it immediately,” Gonzalez said.

Gonzalez also has extra motivation to be America’s ace because he had mud splashed on his reputation in February when his name surfaced in a PED probe. Long story short, he’s the only player from the initial newspaper reports that MLB has told, “Oh . . . never mind.”

Now, six weeks after a surprise out-of-season “probable cause” drug test, Gonzalez can stick out his chest and say, with cause, that he’s the closest thing baseball has to a clean star. Of course, nobody’s certifiable in this era. But Gio looks mighty well-scrubbed. You can bet he’s using the WBC to make a point: This is what my natural nasty stuff looks like, so take that.

As long as their arms can take it, Gonzalez and Detwiler will profit from WBC experience because the tension is excruciating. On Sunday, Torre and his bench looked stricken when Canada had them on the edge of elimination. On Monday, the Netherlands knocked Cuba out of the event. There is no hell like Team Cuba returning to Havana after gagging in the ninth to the Dutch.

Gonzalez and Detwiler are in the WBC fire now. That sounds crazy, but to the players themselves, it’s real: a postseason in the preseason. They chose to turn March into October for the sake of representing their country.

The WBC championship game is next Tuesday in San Francisco. But for the Nationals, the final results will not be known for about seven months.

For previous columns by Thomas Boswell, visit washingtonpost.com/