WASHINGTON -- The Washington Nationals won't be a wild card in the postseason, but Tanner Roark could be.

The 30-year-old hurler continued his second-half turnaround on Sunday, striking out nine and walking none over six strong innings to pick up the W in a 5-4 victory over the New York Mets. Roark's sixth quality start in eight outings since the All-Star break served as further evidence that come October, Washington's starting rotation could very well be the deepest of any contender.

With a double-digit lead in the National League East and barely more than a month left in the regular season, the Nats are all but assured of their fourth division title in six years. When the division series kicks off, their playoff rotation should be anchored by reigning Cy Young Award winner Max Scherzer, who leads NL starters in strikeouts (220) and WHIP (0.85). Behind him is Stephen Strasburg, who ranks among the top five in both WHIP and ERA and has been nails in two starts since returning from the disabled list (12 IP, 7 H, 2 ER, 2 BB, 15 K). After that comes lefty Gio Gonzalez, who's having the best season of his career, ranks third in the NL with a 2.40 ERA and has quietly thrust himself into the Cy Young chat (albeit peripherally). Not too shabby for a big three.

On top of that, manager Dusty Baker has to be feeling pretty good about Roark as his No. 4 starter right about now. After a breakout 2016 campaign in which Roark finished top 10 in the NL Cy Young voting, the burly righty struggled the first half of this season, working to a swollen 5.27 ERA and a 1.45 WHIP. Since the Midsummer Classic, though, he has been a different pitcher, posting a 3.31 ERA and a 1.12 WHIP. At the core of his recent success is an increased reliance on (and effectiveness of) his off-speed stuff.

Known for a sinking two-seam fastball that runs in on righties and away from lefties, Roark has decreased his heater usage in the second half from 58 percent to 52 percent and upped his curveball quotient from 13 percent to 19 percent. Not only is he using his hook more, he's using it better.

"His breaking ball is getting back to form," said Baker, "which is setting up his fastball."

On Sunday night, New York hitters were 0-for-5 with two punchouts against Roark's curve, continuing his recent run of deuce dominance. Since the All-Star break, Roark is limiting opponents to an anemic .074 average with his curveball, down from .231 in the first half, and his whiff rate with the hook has doubled (from 21 percent to 41 percent). In related news, his K's per nine innings has spiked from 7.1 before the break to 9.6 since. Even though the barely recognizable Mets -- who have lost a boatload of players to trades and/or injuries -- weren't exactly the toughest test on Sunday, Roark's uptick has come against some pretty stiff competition: Since the break, he has beaten the Arizona Diamondbacks, Chicago Cubs and Houston Astros -- not to mention the streaking Miami Marlins. As a result, his faith in himself is growing leaps and bounds.

"I wouldn't say 100 percent," said Roark when asked if he's back to feeling like he did last season. "But confidence is a heck of a thing."

The way Roark & Co. have been dealing lately, Baker should have plenty of confidence in them as the postseason approaches.

Since the break, Nats starters lead the NL with a 3.09 ERA, and that's despite the fact that injuries have limited Scherzer and Strasburg to just eight combined starts. Since Aug. 9, Washington starters have a 2.43 ERA; that's more than an entire run better than the next-closest NL team (the Los Angeles Dodgers). But that's not to say there aren't question marks.

First and foremost, Scherzer's first-ever trip to the DL, though seemingly minor, is obviously a concern. Although Strasburg has been sharp since his return, his health history is complicated, and he has made just one playoff start in his career. As good as Gonzalez has been, he has been charmed with runners in scoring position (.138 batting average against) and seems due for some regression. Then there's Roark, whose recent success comes with the small-sample-size tag.

Still, the numbers say that Washington's rotation -- which ranks second in ERA this season behind only the Dodgers (who else?) -- is good. And that it's getting better.

By the time October rolls around, it might even be the best.