(Alan Diaz/AP)

It’s a big loss for the Nationals, who have benefited from Desmond’s breakout season at the plate and leadership on the field and the clubhouse. Outfielder Corey Brown, a left-handed-hitting outfielder, was pulled from a Class AAA Syracuse game and will join the Nationals in New York.

“[Desmond has] been our MVP all year,” utility man Mark DeRosa said. “Big hit after big hit, he’s basically been the captain of our infield for all of the first half of the season so to lose him is tough.”

Desmond has been dealing with an oblique strain since at least June and opted not to attend the all-star game earlier this month to rest the injury. Instead, he returned from the breakand felt the pain return — and it didn’t subside as it had before. All along, Desmond hoped to play with the oblique injury and not land on the disabled list.

While Desmond has managed to play in seven games since the all-star break and notch six hits, he hasn’t had an extra base hit since then — possibly a sign that he wasn’t able to drive the ball with his painful left side.

“At the very beginning, it felt like this,” Desmond said. “And then it loosened up a little bit, and I was able to play through it up to the all-star break. And then I went home and rested. It felt great, at that first initial batting practice back. And then it kind of came back a little bit. I was kind of waiting for it to go away a little bit, like it did the first time, and it just stayed.”

Johnson said the team doesn’t normally give MRI tests to players suffering oblique injuries. But Sunday morning, Desmond received one and the results showed a tear in his oblique area. Johnson said Desmond will rest for two weeks and then test it out; surgery isn’t an option.

After being held out of the starting lineup for five straight games, Desmond returned to it on Friday against the Braves, played the full 11 innings and played both of Saturday’s games. Johnson faulted himself for playing Desmond in both games and not letting him rest.

Desmond said the pain didn’t feel any worse on Saturday but since it had been a long day of playing, he asked to come out of the game. He was pulled from the game after eight innings.

“He’d been playing with it for so long,” Johnson said. “Like he said to me, ‘I’m going to have it all year. I can tell that.’ He was playing so good with it, hitting rockets. I just couldn’t read it.”

Over the past week, the Nationals have already been adjusting to life without Desmond for a stretch. Danny Espinosa moved from second base to his natural position at shortstop, and Steve Lombardozzi moved from the outfield to his natural position at second.

“I was telling Lombo, ‘You can throw away that outfield glove. Put it in the back of your locker,’” Johnson said. “Had a conversation on the bench with DeRosa. ‘Now you’re my backup middle infielder. Your role’s changing. You’re invaluable.’”

Johnson compared Desmond’s oblique injury to DeRosa, who landed on the disabled list earlier this season and missed 50 games. Desmond said he is younger (jokingly calling DeRosa ”an old guy”) and hopes he can return sooner than that.

According to Stan Conte, the Los Angeles Dodgers’ senior director of medical services who has studied the injury, a position player who lands on the disabled list with an oblique injury misses misses an average of 26 days.

Though no official roster move has been announced, Brown was pulled from the first inning of Syracuse’s against the Norfolk Tides. He is headed to New York to join the Nationals, according to a source.

Staff writer Adam Kilgore contributed to this report.