The Nats’ Ross Detwiler fell to 1-2 this season with a loss at Wrigley Field on Wednesday night. (Charles Cherney/AP)

The Washington Nationals have found, in the form of a question, at least one use for the final two months of this season: Should any of their young starting pitchers factor into next season’s rotation? Ross Detwiler, the 25-year-old they drafted with the sixth overall pick in 2007, has consciously decided not to view his starts as auditions. But that’s basically what they are.

Wednesday night, in the Nationals’ 4-2 loss at Wrigley Field to the Chicago Cubs, Detwiler again flashed his promise before a dishearteningly familiar finish. He lasted only five innings, allowing three runs on seven hits while striking out five. Detwiler pitched well enough to give the Nationals a chance to win, a chance squandered a few times by their offense. He just did not pitch very long.

“It was just okay,” Manager Davey Johnson said. “I’d give him a C-plus.”

Detwiler is tall (6 feet 5), strong-armed (his fastball hit 94 mph Wednesday) and left-handed. But in his nascent major league career, Detwiler has not translated his potential into the mold of a starting pitcher capable of taking the ball deep into games. Detwiler has made 22 career starts. He has pitched six innings in six of them and seven innings only once, in 2009.

Then again, Detwiler is also 25. And he has not had an easy assignment recently. He toggled between long reliever and starter, which Detwiler said has not bothered him — “I think I’m over that,” he said. Since the Nationals inserted him into the rotation on Aug. 4, his two starts have come at Coors Field and Wrigley Field — a launching pad and bandbox. Now, then, is not the time for sweeping judgment.

“I think he can do it,” Nationals pitching coach Steve McCatty said. “He needs to trust himself not to get so much on the corner, but to make quality pitches. Get some swings and groundballs and pop-ups.”

Clearly, Detwiler is talented enough to retire major league hitters. In 10 innings as a reliever this year, Detwiler allowed two earned runs and struck out nine. “He shows a good fastball. He’s got good control. He mixes his pitches well,” said Jayson Werth, who hit 14th homer in the sixth inning. “He’s got a lot of promise and a lot of potential.”

The trick for Detwiler is proving he can retire batters multiple times on the same night. Wednesday, Detwiler mostly cruised through three innings. The Nationals gave him an immediate lead. Ryan Zimmerman singled in his first at-bat to extend his hitting streak to 18 games, the longest in Nationals history aside from his 30-gamer in 2009. He scored when Cubs shortstop Starlin Castro made a wayward throw to second on Michael Morse’s groundball.

Detwiler allowed a leadoff home run down the left field line to catcher Geovany Soto in the second, helped by the breeze blowing out to left. But he recovered from that misplaced sinker to retire the side in order from there. He mowed through the third inning, too, surrendering only a single and striking out two.

But the more an offense sees Detwiler, it seems, the greater their odds at success against him. Soto walked in the fourth. With two outs, Alfonso Soriano popped up deep down the right field line.

Werth had played Soriano to pull, which gave him a long sprint across the outfield. A sliver of dirt separates the foul line and the brick fence alongside. Werth had to slow up and slide just before he reached the wall, and he could reach the ball. He perhaps could have prevented Soto from scoring had he tried to gather the ball on a bounce on his feet rather than sliding out of self-preservation. Instead, the ball hopped over him and he had no chance.

“If there’s 15 feet of foul ground, I might have a play on it,” Werth said. “If there’s more ground over there, do I catch it? I still don’t know. But I’m not going to run full speed into the wall. It’s just one of those things. You got to put yourself first sometimes out there and try to make the play. That was just one of those well-placed baseballs.”

The Cubs had taken a 2-1 lead, but Detwiler minimized the damage. Following a single by Cubs starter Rodrigo Lopez, Detwiler struck out Castro.

But Detwiler faded in the fifth. Reed Johnson led off with a home run to left-center, one of his four hits Wednesday night. Both Aramis Ramirez and Soto smoked balls to the warning track. Werth caught both, but by his 84th pitch it had become clear Detwiler had little left.

“In this ballpark as a young pitcher,” Johnson said, “I’m not going to let him get beat up.”

There will be another chance for Detwiler. Five days from now, Johnson will give Detwiler another chance at proving he belongs in the rotation. The Nationals know he is young and talented. They still need to find out if he can be something more.