(John McDonnell / The Washington Post)

The Nationals will place struggling right-hander Dan Haren on the disabled list with shoulder stiffness, an injury Haren said has not been a major factor in his horrendous season in Washington. Haren underscored what he believed to be the nature of his injury when a reporter asked him what had sent him to the DL. “I don’t know,” he replied. “What’d they say?”

The Nationals have become convinced Haren’s physical ailments have led to faulty mechanics and the worst season of Haren’s distinguished career. Haren is 4-9 with a 6.15 ERA, the highest in the majors, while allowing a league-worst 19 home runs. He admitted he has had trouble getting his shoulder loose recently.

“My shoulder’s been bugging me the last two, three starts,” Haren said. “Nothing really major at all, nothing I haven’t pitched through in the past. I’m not really concerned about it, but they wanted me to take some time to get 100 percent. But I definitely don’t want to use this as an excuse for the first three months of the season. That was more due to lack of execution, instead of an injury.”

Haren will rest and take either anti-inflammation medication or receive a cortisone shot in his right shoulder. He plans to receive an MRI in the next day or two to rule out a serious injury, but he does not believe he has suffered any structural damage.

“I think I would’ve rather just keep pitching, yeah,” Haren said. “But from a team standpoint, we talked it over this morning for a while, and they want me to get back to 100 percent. That said, a lot of starting pitchers, most starting pitchers, aren’t pitching at 100 percent. There’s always some dings, some aches and pains, but in my case they wanted me to get back to feeling 100 percent, so they wanted to give me some time, to get my shoulder loosened up a bit, I guess.”

Haren worried in his fourth and final inning Saturday that his velocity was decreasing significantly. His fastball sat that inning between 86 and 89 mph. He finished the start having allowed six earned runs in 3 1/3 innings.

“He’s a gamer,” Manager Davey Johnson said. “He wasn’t particularly pleased to go on the disabled list, but he knew it was probably the best thing.”

Last season, Haren landed on the DL for the first time in his career with lower-back stiffness. Though the Nationals worried hip and back issues may have led to Haren’s mechanics unraveling, Haren said his back is not a problem.

“My back feels better right now than it did at any point last year,” Haren said. “My hip has never been an issue. I’ve never missed any time for it. My hip’s been hurting since I was in Oakland, but it’s nothing that’s going to go away, it’s just there. My back feels great, though. I don’t know, maybe I was compensating a bit in my shoulder, not getting loose or whatever. But overall I don’t feel that bad health-wise. Hopefully this will be a little time, and then back.”

In the meantime, the Nationals will need to find a starter to replace him. Ross Ohlendorf may be a candidate after he allowed two earned runs in 10 2/3 innings over two appearances, a spot start in Colorado and mopping up for Haren. Johnson, though, indicated he wants to keep Ohlendorf in a long-relief role.

“We’ve got a couple guys we’re real high on that we may give an opportunity up here,” Johnson said. “There’s also the opportunity to use Ohlendorf in that role, but don’t really want to put a younger pitcher in the bullpen and put him in a long relief role.”

The most compelling candidate to replace Haren may be Class AA Harrisburg right-hander Taylor Jordan, who has been a revelation since the spring, when he wowed Nationals evaluators in Viera, Fla. In 14 appearances this season, which he started at Class A Potomac, Jordan is 8-1 with a 0.95 ERA, having struck out 71 and walked 14 in 85 1/3 innings.

Taylor has made only seven starts above Class A, but the Nationals have not shied away because of inexperience in the past – they summoned Nate Karns this year despite him having made only nine starts above Class A.

One rival scout who follows the Nationals’ was asked if he felt Jordan was ready to pitch in the majors. He replied, “Will throw strikes, not afraid to challenge hitters with fastballs. Yes.”

The Nationals would not need another starter until Saturday. Jordan is scheduled to start Monday at Class AA Harrisburg, which would put him in line to pitch again Saturday. Jordan is not on the Nationals’ 40-man roster, but the Nationals could open a spot by transferring Ryan Mattheus to the 60-day disabled list.