At the trade deadline in 2010 Tanner Roark amounted to what baseball people call “inventory” — a spare arm to suck up innings in the bushes. It only took a journeyman infielder for the Washington Nationals to pry him and another Class AA pitcher from the Texas Rangers. Roark refused to the let the label stick. He climbed up the Nationals’ farm system. He earned an invitation to major league spring training. He joined the Nationals’ bullpen and in long relief he pitched like a sorcerer.

What the Nationals have now in Roark they aren’t exactly sure but in the final month of a lost season they intend to find out. Saturday night Roark led the Nationals to a 9-2 victory with six scoreless innings in the first start of his major league career a masterful four-hit buzz-sawing of the Miami Marlins. With Bryce Harper scratched 10 minutes before first pitch Ryan Zimmerman’s two home runs and a spectacular play at third base led the Nationals’ support of Roark.

Friday afternoon Roark said he would take a simple plan into his first start: “Don’t try to change anything.” With red socks pulled high and black hair flowing out the back of his cap Roark marched to and from the mound with a stoic unchanging expression. The 26-year-old right-hander attacked with a low-90s fastball and a barrage of strikes. He retired the first nine hitters he faced walked none struck out four and chucked only 71 pitches. His outing suggested he had done this before even though he had not.

“Yeah I’m a little surprised” Roark said. “But I don’t want to change anything. I just want to be the same old person I’ve always been and keep going right at guys.”

Saturday morning Baseball Prospectus pegged the Nationals’ postseason odds at 0.6 percent and they grew dimmer when the Cincinnati Reds won again in the afternoon. With 21 games left the Nationals still trail the Reds by eight games for the second wild-card spot. Manager Davey Johnson insisted he had not shifted focus away from a miracle playoff run. But the Nationals really can start trying to answer questions for next year.

“I knew I had something” in Roark Johnson said. “He’ll make his next start. I’m not that stupid.”

Roark trying to shove his way into consideration for a rotation spot may be one revelation. After his six scoreless innings Saturday Roark owns a 0.94 ERA 28 2 / 3 innings into his big league career. The Rangers wish they had gotten that much out of Cristian Guzman.

“Ever since he’s come up everything he’s done has been impressive” Zimmerman said. “He trusts his stuff and he knows what he wants to do. If you have a plan it doesn’t really matter where you’re at.”

Shortly after Roark’s promotion Aug. 7 Johnson came to believe Roark deserved to start. Ross Ohlendorf would not stop tiring after five innings and Roark became the better option. He had punched up a 1.19 ERA as a long reliever. He needed only 13.8 pitches per inning more efficient than any qualified starter in the majors. He fired his fastball up to 95 mph and peppered the edges of the strike zone.