(AP Photo/Alex Brandon)

The Nationals placed left-hander Gio Gonzalez on the disabled list with left shoulder inflammation, but they received good news after an enhanced MRI exam revealed no further damage and confirmed Gonzalez will require only rest.

Gonzalez underwent an enhanced arthrogram MRI exam Sunday morning, General Manager Mike Rizzo said. The Nationals placed Gonzalez on the disabled list regardless of the findings because the MRI exam includes an injection of dye, and the injection alone sidelines a pitcher for two starts.

“The level of concern, we’ll find out more about it today,” Rizzo said early Sunday. “I don’t have a great concern level for it right now, because of the way Gio said he felt after the game.”

Rizzo’s optimism was validated once results came back, Manager Matt Williams confirmed following the Nationals’ 6-3 victory Sunday. Gonzalez will not require any kind of procedure, and he will likely return after a minimum or near-minimum stint on the disabled list. He will rest for four or five days, Williams said, then begin a throwing program.

Gonzalez exited his start Saturday after he allowed five runs in three innings, his second consecutive lousy outing. Gonzalez said he had trouble finding a consistent arm slot, a potential symptom of a shoulder injury.

Despite awful results in Gonzalez’s last two results, Rizzo did not suspect Gonzalez was hurt. Both scouting and analytical data — his arm speed, the “spin rate” of his curveball, the velocity of his fastball — all seemed normal, Rizzo said. Gonzalez had trouble with command, but that is not atypical for Gonzalez. Afterward, Gonzalez passed a strength test administered by Nationals trainers.

But after a start in which his ERA rose to 4.62 from 2.91 just a week ago, Gonzalez said he felt “beyond normal soreness,” Rizzo said. On April 23, Gonzalez exited a victory over the Angels after five innings with shoulder stiffness. Those two events convinced the Nationals that Gonzalez needed further evaluation.

“We felt this is the prudent way to do it,” Rizzo said. “Get him the arthrogram, so we see exactly what’s going on in there. Shut him down for 15 days. Get him some rest and relaxation. Once we find out what’s on the MRI, we’ll take it from there.”

In his seven-year career, Gonzalez has been one of the most durable pitchers in baseball. He had never previously landed on the disabled list, and he has thrown at least 195 innings in four straight years. Having never experienced a serious injury, Gonzalez was subdued late Saturday night.

“He was bummed out a little bit and depressed,” Rizzo said. “But that’s his personality. He wants to help the ball club. He’s a great team guy. He knows if he misses any kind of time, he’s a vital part of this club. This is something that’s new to him.”

It is not clear who will take Gonzalez’s place in the rotation. The likeliest candidate is hard-throwing Class AAA right-hander Blake Treinen, who has allowed one earned run in 11 2/3 big league innings this season. The last time the Nationals needed a spot start, they tabbed Treinen, and he matched Clayton Kershaw for four innings before a collapse. Treinen started Friday for Syracuse, so he would be fully, but not overly, rested.

The Nationals, Williams said, may also turn to Taylor Jordan, an exiled member of their opening day rotation. Jordan has allowed one run in 11 innings over two Class AAA starts since his demotion. The velocity of his fastball, which dropped to the high-80s this season, has returned to 94 miles per hour.

“We haven’t decided yet,” Rizzo said.

Less than 10 days after the Nationals’ rotation became whole with Doug Fister coming off the disabled list, Gonzalez, the cheerful lefty who won 21 games and finished third in the 2012 Cy Young vote, is going on it. The Nationals have also lost Ryan Zimmerman, Wilson Ramos, Bryce Harper, Adam LaRoche, Denard Span and Scott Hairston to the disabled list at various points in the season’s first 42 games.

“We don’t talk about the injuries,” Rizzo said. “It’s part of baseball. That’s why you build depth in the organization. We’re not going to alibi. We’re not going to use it as an excuse. We’ve got our 25. This is our 25. We’re going to go to battle with those guys. It’s time for guys to pick up the slack.”

The Nationals called up reliever Ryan Mattheus as a temporary replacement on their active roster. Mattheus has already been called up and sent back down to Syracuse once this season.

“You don’t know if you’re going back after the game. You don’t know if you’re going back in two weeks. You don’t know if you’re ever going back,” Mattheus said. “But you try to keep that out of your mind, and just try to go out and pitch. That’s what you try to focus on, and not the shuttle back and forth.”