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The Nationals answered the first major question about the composition of their pitching staff in surprising fashion Monday, shifting incumbent fifth starter Ross Detwiler to the bullpen and leaving a competition for the final spot in their rotation between a pair of rookies and, perhaps, a veteran who did not pitch in the majors last season.

The Nationals scheduled Detwiler to pitch an inning in relief of Taylor Jordan on Wednesday, the first indication that Detwiler, the sixth overall pick in the 2007 draft, will begin the season in the bullpen. Manager Matt Williams informed Detwiler in the morning and confirmed the decision to reporters in the afternoon.

Detwiler was “not happy,” Williams said. “But I wouldn’t expect him to be.”

“We feel like it’s a good move for our team,” Williams added. “He provides something special out of the bullpen for us. I don’t know if anybody would ever be really happy with something like that. We don’t feel like it’s a demotion of any sort. We just feel like we’re a better team with him coming out of our bullpen. He offers something that’s special  power lefty, mid-90s lefty. It doesn’t mean he won’t start at some point in the future.”

Williams has been planning to finalize the Nationals’ regular-season rotation by Tuesday, an off day for the team. Monday morning in Viera, Detwiler and pitching coach Steve McCatty chatted for several minutes in the Nationals’ clubhouse.

Detwiler, whose Game 4 start in the 2012 NLDS stands as perhaps the most clutch pitching performance in Nationals history, began last season entrenched as the team’s fifth starter. He pitched well before he suffered a back injury in early May and, after stilted attempts to return, ultimately had back surgery.

The injury and the arrival of Doug Fister thrust Detwiler into a fight for his job. When he arrived at spring training healthy and hitting the mid-90s with his fastball, he seemed likely to hold on to his spot in the rotation.

But the Nationals have considered Detwiler a potential weapon out of the bullpen since last fall, and his style may fit better in relief. Detwiler’s threw fastballs for 88 percent of his pitches last season. His reliance on one pitch allows hitters to time the pitch and has prevented him from pitching deep into games. In his career, hitters facing him for the third time in one game have hit .324 against him. In 69 starts, Detwiler has pitched into the seventh 21 times and into the seven times.

In limited experience, Detwiler has thrived out of the bullpen. In his career, Detwiler has allowed four earned runs in 32 1/3 relief innings, holding hitters to a .173 batting average. Last fall, one Nationals official compared Detwiler’s possible impact to Pirates left-hander Justin Wilson, a former starter who in 2013 posted a 2.08 ERA over 73 2/3 innings.

Williams could use Detwiler in a variety of roles, he said, ranging from one-out appearances to long relief. Detwiler’s sinking fastball, success against left-handed hitters and durability coming from a starting role will allow Williams options in how to use him.

“I see him as a power lefty out of the bullpen,” Williams said. “If we get in a matchup where if we’ve got two out of three guys facing that inning are lefties, we can certainly use him for a full inning in that regard. We could also use him for multiple innings. I wouldn’t limit him to a lefty specialist role. I just think it’s a luxury for our team to have a guy in our bullpen who can do those types of things.”

With Detwiler headed to the bullpen, Williams said, the Nationals’ fifth starter competition will likely come down to Jordan and Tanner Roark, two rookies who impressed in cameos last season. Williams also declared 6-foot-10 veteran Chris Young, who is in camp on a minor league deal, as a candidate. While Young has more experience, he is coming off a bout with thoracic outlet syndrome that sidelined almost all of last season. Young has also allowed four earned runs in eight innings.

Jordan, 25, dazzled the Nationals last year in spring training, his first after recovery from Tommy John surgery. He produced groundballs by the bushel in nine starts, and improved offspeed pitches have helped him increase his strikeout total this spring. Jordan has allowed seven earned runs in 10 innings on 16 hits and no walks, striking out 13.

In a revelatory September call-up, Roark went 7-1 with a 1.50 ERA. He had been scheduled to make his next start Monday in a game rained out, and will start in a minor league game Tuesday. Roark has allowed four earned runs in eight innings, striking out six and walking two.

“I’m just going stay within myself, like I always have,” Roark said. “Be confident, go out there, keep competing.”

Detwiler, 28, provides a second lefty reliever to pair with Jerry Blevins, whom the Nationals acquired in a trade with Oakland this winter. That would seemingly squeeze lefties Xavier Cedeno and Michael Gonzalez out of the competition for the opening day roster. Williams, though, said he could envision carrying three left-handers in the bullpen, and the final relief spot remains up for grabs by both lefty and right-handed relievers.

“That’s open for discussion still,” Williams said.

The chance for Detwiler to start, though, has been closed. The Nationals helped their dearth of left-handed relief options when they traded for Blevins. They declined to match the salary for several free agent left-handed relievers, though, which left open the possibility of shipping Detwiler to the bullpen.

Usually, starters convert to relief because they failed. The only misstep Detwiler made since the best postseason start in team history was getting hurt. Detwiler will now have to swallow his disappoint and accept a new role.

“We told him, this is something that is going to make our team better,” Williams said. “We’re here to win games and to compete in meaningful games in September and October. And he’s going to be a major part of that out of our bullpen.

“For me, it’s not a tough decision. It’s a prudent one. It’s not a question of doing it off the cuff. There’s been a lot of thought, a lot of talk amongst our staff, in making that move. If I know Ross, he will take that bull by its horns, and he’ll be really good.”

James Wagner contributed to this report.