(Scott Cunningham / Getty Images)

ATLANTA – The Nationals’ preponderance of injury, a trend plowing into its second year, reached a cruel apex Saturday as they placed one phenom picked first overall on the disabled list and awaited MRI results on another.

The Nationals placed Bryce Harper on the disabled list with left knee bursitis, trying to finally scuttle the swelling and soreness in the joint following two weeks in which Harper toggled in and out of the lineup in the wake of his collision with the outfield wall at Dodger Stadium. The Nationals called up 26-year-old right-handed reliever Erik Davis to take his roster spot.

Back in Washington, an MRI performed on Stephen Strasburg a day after he left a start after two innings revealed a “slight strain kind of up his back and the right side,” Manager Davey Johnson said. The Nationals have not ruled out Strasburg making his next start, Johnson said, but given the nature of oblique injuries – the term the Nationals gave Strasburg’s ailment Friday night – that would seem to be either bold optimism or needless risk.

“We’ll see how he feels,” Johnson said. “We have that off day [Monday], so we could push him back. If he’s not having any discomfort and it’s not grabbing him, he wouldn’t miss a start. But if it’s bothering him, he’ll probably miss a start and see if that eases up for him and they don’t have to do anything more for that. But that’s the old method of taking care of somebody that had something bothering him.”

The Nationals would be able to bump Strasburg’s turn in the rotation to June 8 before they need another starter. Johnson said Craig Stammen, who pitched four perfect innings Friday in relief of Strasburg, would be a candidate to replace him. But if Ross Detwiler can return after his own bout with an oblique strain, the Nationals may be able to slide Nate Karns – Detwiler’s replacement – into Strasburg’s spot.

“There’s too many variables to be deciding who’s starting where four or five days from now ,” Johnson said.

Johnson has been juggling variables often this year. The Nationals are currently playing with Jayson Werth, Wilson Ramos, Harper, Detwiler, Ryan Mattheus and Christian Garcia on the disabled list. Ramos had already spent one previous stint on the disabled list, and Ryan Zimmerman missed 15 days in April. That list does not include Danny Espinosa, who has scuffled through a tear in his left rotator cuff and a bone chip in his right wrist.

“Every year you deal with something, but it seems we’ve had more than normal this year,” Zimmerman said. “But there’s not much you can do about it. You got to play with what you got and hope you can win some games and make some headway before all these other guys get back.

“The more injuries you have, the harder it is to deal with. Big league guys aren’t just sitting around waiting to come play in the big leagues when other guys get hurt. It shows you hard it is to be consistent at this level. It’s not easy to find people to do that.”

No player may be more difficult to replace than Harper, a 20-year-old hitting .287/.386/.587 with 12 home runs. The Nationals have gone 3-9 when he is not in the starting lineup. Harper crashed violently into the Dodger Stadium fence May 13, then returned as a pinch hitter two nights later. Harper returned to the lineup, aggravated his knee and tried to come back three times before last Sunday, when he fouled a ball of his left knee.

Werth talked with Harper by phone on Friday night and could hear his frustration with the nagging bursitis. Werth dealt with the same injury in 2005 and learned that the key to solving the injury is resting the knee to calm down the swelling. Even with the injuries to Harper and Strasburg, among others, Werth was still optimistic that the team’s fortunes can change.

“We’re OK,” he said. “We’re in a good spot. We still haven’t hit our stride at any point this year. A lot of the season left. We’re fine. We’re in a good place. We’re a good club and as the season goes on we’ll put it together and hit our strike and not look back. It’s been frustrating for everybody. We’re behind the eight ball with injuries. It seems like we pitch, we don’t hit, then we hit, we don’t pitch.”

The Nationals still referred to his injury as a “day-to-day” matter. But they decided after Harper has missed five straight games they need to exercise caution. Harper, who was not available for comment, will be eligible to return June 11.

“If the club felt like he would be ready to come back in three or four or five days, we wouldn’t have DL’d him,” Johnson said. “But I think in talking to Bryce, we’ve got to get by this where it’s not a recurring thing and he’s not going out there and playing 80 percent. Because his legs are just as much a part of his game. Taking that extra base, running hard, I don’t want to handicap him that way, and the chance of him getting injured further. So everybody looking at it said that’s the best thing to do for him.”

That raises an obvious question: Would it have been the best thing to simply place him on the disabled in the aftermath of running head-long into a wall?

“Well, you just don’t know how bad the injuries were,” Johnson said. “He felt all right. Really, he felt pretty good the next day. He had some bruises but didn’t have any swelling. And when he went back to playing and he dove for a ball and then he slid head-first, I think it was probably a sensitive area and he exacerbated it by pounding on it more. So he felt good enough and he wanted to play, and he knows his body better than anybody. But I think it was probably a little injury and diving for a ball in right field and then going head-first into third didn’t help it.”

The Nationals believe Strasburg’s injury will not be as problematic as Harper’s. Friday night, before his MRI, Strasburg said he believed he would not need to miss a start.

“A lot of times, tightness in muscles, rest a little and it loosens up and you’ll be fine, good to go,” Johnson said. “So I’m hopeful that we’re not having a lingering problem with Stras.”

Frequently over the past two seasons, though, the Nationals have predicted a quick return only for an injury to force a player to the disabled list. In early May, Werth felt a hamstring tweak and the Nationals said he could return in a matter of days. Werth has not played since May 2. He aimed to play nine innings Saturday night at Class A Potomac and could return Tuesday.

The Nationals had hoped Detwiler would miss one start at most when he strained an oblique during his start May 15 in Los Angeles. They placed him on the disabled list 11 days later, and Karns will pitch in his place for the second time Sunday. Detwiler played toss and jogged in the outfield today, and he said he has not exact timetable for a return.

“I felt nothing today,” Detwiler said. “If I felt anything, I’m under the strict order to shut it down. I did not shut it down today.

“I’m not allowed to do my job,” Detwiler added. “Anytime they take something away from you that you love, it always gets pretty tough.”

Plenty of his teammates know the feeling. The Nationals, 4½ games behind the Braves at first pitch Saturday night, have tried to soldier forward. Their reserves excelled last year, and this year they have faltered. With their health problems only growing, they can only hope that will change.

“It’s tough, but adversity gives opportunity to other guys and they get a chance to show how good they are,” Johnson said. “And that was our strength last year with all the injuries that we had. Guys stepped up. Of course, Harper was the one that came in when Werth went down. Got to step up. That’s what you got to do.”