"RAAAAAR! I STRIEKZ OUT UR SIDE!" (Not an actual quote.)
Rizzo may have been on to something with his moves to improve the pitching staff this season. He traded a pile of prime prospects for Gio Gonzalez, signed free agent Edwin Jackson, and made the tough choice to give Ross Detwiler the last rotation spot, consigning John Lannan to AAA to start the season. He even took a flier on veteran reliever Brad Lidge to reinforce the bullpen, which has made him look like a mind-reader after Drew Storen's elbow issues. How has it payed off? So far, awfully well. Let's look at some numbers.
After last night's low-scoring, 13-inning game, the Nats currently have the lowest ERA (1.92) in the league. Their ERA- is 53, meaning they allow just over half as many runs as a league-average pitching staff after you correct for ballpark effects (average is 100, lower is better). Luck, you say? They're only slightly outperforming their fielding-independent pitching (FIP), which is 2.18--best in the NL by nearly an entire run!
After the jump, a look at their peripherals and some other indicators of whether the Nats have just been lucky on the mound or if they're actually awesome.
The Nats are fanning a ton of batters, despite pitcher claims of pitching to contact: they are striking out 25.8% of all batters faced (9.48 K/9), which is 2nd in the NL. They have the 2nd most Ks in the league (79). Mind you, they're walking 9.2% of batters (3.36 BB/9), which is only middling. As a result, team WHIP is a "mere" 1.03, 2nd best in the NL. Starters have been going deep into games, averaging 6.0 IP/GS so far (4th in the NL). Relievers have been good, too, collecting 12 shutdowns (3rd most) and only having 3 meltdowns (tied for 3rd fewest) in 25 appearances.
Is this sustainable? Well, it's an awfully small sample so far, only 8 games and about 300 total batters faced. Let's look at some of the measures of "luck" for pitchers. Team ERA is slightly better than team FIP, and the fielders are converting 73.2% of batted balls into outs (a bit better than NL average 70.6%). Team BAbip against (a rough measure of "luck" with hits falling in) is .265, which is only slightly better than league-average (.270). Likewise, the staff strand rate (which you can think of as "luck" with how baserunners get either clumped together or scattered across innings during a game) is 78.6%, again slightly better than league-average (76.5%). However, their league-leading 0.12 HR/9 is what's really helping: their xFIP (which factors out "luck" in terms of fly balls going for HRs) is more than a run higher than their ERA, though it's still 2nd best in the NL.
Bottom line: Nats pitchers are killing it so far. Even after factoring out some good luck and good defense, they're still at or near the top of the NL. Mind you, they probably won't stay as dominant as they have been so far once more fly balls start going over the wall. Our preliminary verdict: a bit lucky, but mostly awesome.