As the Baltimore Orioles came to bat in the eighth inning here on Sunday, they saw a scoreboard bearing a familiar ugly sight for teams that face the Washington Nationals: a “0” beside their team’s name.

After 70 games, the Nats not only lead the majors in ERA at 2.95, but they lead it by a huge and startling margin. Nobody is close. Only one team is less than four-tenths of a run behind. And most clubs are so far behind you can’t see them over the horizon. The Nats’ ERA is more than a full run lower than either the major league (3.98) or National League (3.96) ERA.

However, as the Birds came to bat, they also saw another recurring sight. All that exceptional pitching rarely gives the Nats more than a tiny margin for error. Their lead was as small as the rules allow, 1-0. More times than not, the first-place Nats, 41-29 after going 18-14 in 32 straight games against AL East and NL East teams, have held on to win.

But sometimes they crack. Or get smashed. This time, lefty Sean Burnett, a symbol of all the Nats pitchers who have done more than expected, who’ve stepped into new roles or simply pitched better than they ever had before, did not have the right answer. A single by Adam Jones and a homer by Matt Wieters, both likely all-stars, were enough for a 2-1 Baltimore win in the rubber game of a series that had a total score of 5-5.

Such series come and go, even between Beltway rivals. But the theme of the Nats’ season has become one of the most powerful in baseball: an incredibly deep, competitive pitching staff, young but devoid of self-pity, has ignored its team’s offensive problems and kept the Nats atop the NL East on the strength of arms and defense.

How good are they? Or, at least, how amazing have they been so far?

ERA+ is the best single statistic for measuring the excellence of a team’s pitching staff. It adjusts for the run-scoring levels of different eras and also factors in the influence of a team’s home ballpark. It’s not perfect, but it’s really good. And it seldom lies. The Nats’ current ERA+ is 135, which means, adjusted for fairly neutral Nats Park, they are 35 percent better than the major league norm in 2012. Where does that stand?

If the Nats maintain their current pace, they would have the second-best ERA+ in more than 100 years, second only to the 1926 Philadelphia A’s led by Hall of Famer Lefty Grove and 247-game winner Jack Quinn. The other teams in the top half-dozen over the last century (excluding World War II years) are the ’39 Yankees (Red Ruffing, Lefty Gomez); the ’97 and ’02 Braves of Greg Maddux, Tom Glavine and John Smoltz; and the ’54 Indians with Early Wynn, Bob Lemon, Bob Feller, Hal Newhouser (all Hall of Famers), and relievers Don Mossi and Ray Narleski. Talk about being in good company. (For the record, the Cubs of 1906 were the best since 1901.)

“We plan on doing this the whole year,” GM Mike Rizzo said after he was told his staff might have a chance to rank among the best ever.

As irony would have it, the Nats’ next four games are in Colorado, the worst pitchers park in generations. But after that, sanity should return.

“They have all been great. When you have talent, work quick, challenge hitters, strike out a lot of guys and have good defense behind you, that always works,” said pitching coach Steve McCatty. “This is a power-arm staff, but with great off-speed pitches that can strike people out inside the zone, not just on ‘chase’ pitches.”

“We’re not trying for strikeouts, but this staff can’t avoid them,” he added. “I can’t say enough about their tough mentality. They don’t worry about how many runs we score, just about how many we give up. Control what you can control.”

Anything else, Cat? “Yeah, you haven’t seen the best of ’em yet. They’re all young and they’re all still learning. They enjoy each other and analyzing the game.”

The Nats have certainly worked against early-season headwinds. Of their 70 games, 45 have been against teams ranked in the top half of the sport in offense. Of their last 50 foes, 39 have records over .500, not counting six with the Phils, who won 102 games in ’11.

“We’ve got unbelievable pitching. A lot of teams are noticing. How can they not?” said Tyler Clippard, who has been 12 for 12 in save opportunities with one hit allowed. “It’s fun to be part of. Our starters, two or three runs are the most they ever seem to give up.”

It’s actually better than that. Most teams value “quality starts” — a minimum of six innings and no more than three runs allowed. The Nats have 47 of those. But that demands only a 4.50 ERA or better. Why not raise the bar? Why not demand a “high-quality” start that requires an ERA of 3.00 or less? Even three runs in eight innings wouldn’t be good enough. The Nats now have an amazing 42 of those, including Ross Detwiler’s five scoreless innings Sunday in his first start since he was moved back into the rotation.

The ERAs of the starting rotation of Stephen Strasburg, Gio Gonzalez, Jordan Zimmermann, Edwin Jackson and Detwiler are 2.46, 2.55, 2.89, 2.91 and 3.09. Everybody talks about that. But relievers Craig Stammen, Burnett, Ryan Mattheus and Clippard have a combined 1.73 ERA in 120 innings. And Drew Storen is coming back.

“Around the rest of the [baseball] world, three runs in six innings seems pretty good,” said one Nats official. “Around here, it’s not. [Our] margins are small. But our pitchers seem to thrive on it.”

How long will that last? “It’s a lot easier to pitch with a three-run cushion, that’s for sure. We don’t give ’em much margin. I tip my hat,” said Manager Davey Johnson. “It’s my job not to overwork ’em.”

More runs would help, but the Nats’ staff isn’t expecting them — yet. “It’s still early. But what we’ve done so far is such a positive. When we get to August and September [when Jayson Werth returns], then what if we hit our stride [offensively]?” asked Clippard. “We can be dangerous. That could be something.

“We just have to keep our heads down. One day at a time.”

Can the Nats keep it up? Will their arms stay healthy or not? Let all of that take care of itself. What this staff has already accomplished deserves praise and perspective. You could live 10 lives in 10 baseball cities and never see pitching as consistently exceptional, relative to the standards of the era, as the Nats have provided so far. That’s fact.

It would seem intemperate to anticipate too much more of the same. But these Nats like rash. As McCatty loves to say, “Never work away from the bat.” Challenge it.

“This,” said Rizzo, “is who we think we are.”

For previous columns by Thomas Boswell, visit