According to MLB.com's Bill Ladson, Gonzalez becomes the seventh Nationals player to be placed on the disabled list in 2014:
"The Nationals on Sunday placed left-hander Gio Gonzalez on the 15-day disabled list because of left shoulder inflammation and recalled right-handed reliever Ryan Mattheus.
"Last Sunday, Gonzalez had an MRI that revealed on structural damage and confirmed the inflammation in the shoulder, according to manager Matt Williams.
"Gonzalez becomes the seventh major player -- Ryan Zimmerman, Bryce Harper, Adam LaRoche, Denard Span, Wilson Ramos and Doug Fister -- on the 25-man roster to go on the DL this season.
"'I spoke to him late (Saturday) night. He was bummed out a little bit, depressed,' general manager Mike Rizzo said about Gonzalez.
"'That's his personality. He wants to help the ballclub. He is a great team guy. He is a vital part of this club. He has never been on the DL before. It's something that his new to him.
"Gonzalez has been dealing with shoulder problems dating back to his April 23 start against the Angels, but he said it was nothing to be concerned about.
"However he had one of his roughest starts Saturday in a 5-2 loss against the Mets, allowing five runs in three innings. After the game, he declined to discuss his shoulder problems, saying he had to gut it out on the mound.
"'It's one of those things you've just got to grind through,' Gonzalez said. 'I'm just trying to find out what it is, and hopefully something positive comes out of it.'"
Marc Lancaster of The Washington Post adds more details about Gonzalez's injury:
"General manager Mike Rizzo said before Sunday's game that Gonzalez was having an MRI arthrogram on his shoulder -- a more detailed process than a normal MRI that involves dye being injected into the affected area.
"Because Gonzalez isn't allow to throw for five days after the procedure, the Nats decided to play it safe and shut him down for two weeks even before receiving the results of the MRI.
"'Approximately a month or so ago we pushed him back a start because he had a little soreness then, and felt better throughout the starts.'
"'Yesterday after the game he complained that it was barking a little bit, it was a little bit beyond normal soreness for him after a game.'
"Rizzo said he doesn't have a 'great concern level' about the prognosis because Gonzalez's arm speed, velocity and rotation rate on his breaking balls have looked normal recently."
The Washington Post's Adam Kilgore weighs in on who will replace Gonzalez in the Nationals' rotation:
"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."
The 28-year-old Gonzalez has 963 strikeouts and a career 3.64 ERA in 981 innings pitched for the Oakland Athletics and Nationals, per ESPN stats.