For the second straight season, Trevor Williams is going on the injured list with an arm issue. And the veteran right-hander didn’t sound overly optimistic about his latest ailment.

The Nationals placed Williams on the 15-day IL with a right elbow sprain, the most significant of a series of transactions the club made this morning prior to its Fourth of July matinee against the Red Sox. The team also activated catcher Keibert Ruiz off the 7-day concussion IL, optioned Drew Millas to Triple-A Rochester and recalled reliever Ryan Loutos only one day after sending him down.

The Williams injury revelation comes two days after the 33-year-old labored through the worst of his 17 starts this season, one in which he threw 54 pitches in a six-run top of the first against the Tigers and then returned to toss two more innings before manager Davey Martinez pulled him in the first game of a day-night doubleheader.

Williams said his arm didn’t respond as it normally does after a start, so he notified club officials about it Thursday and underwent an MRI. He suggested the team is still waiting to fully decipher the results of that test before determining a course of action, but the right-hander concedes he’s going to miss some time.

“It’s hard to pinpoint exactly,” he said. “It could be a mechanical deficiency. It could be a grip thing. Who knows? The unfortunate part is that the MRI showed I’m not going to be able to start this weekend. We’ll see what happens and what the next steps will be.”

One of the best defensive plays Andrew Chafin has made in some time wound up sending the veteran reliever to the injured list.

The Nationals placed Chafin on the 15-day IL this morning with a right hamstring strain, an injury he sustained six days ago while doing the splits to make a play in the field. Ryan Loutos, a right-hander acquired only four days ago from the Dodgers, was recalled from Triple-A Rochester to take Chafin’s place in the bullpen.

Chafin didn’t initially show any ill effects when he sprinted to cover first on Corey Seager’s grounder to the right side in the top of the ninth Sunday against the Rangers, then stretched to the point he was doing the splits to snag CJ Abrams’ return throw on the 3-6-1 double play. But the left-hander did not pitch in any of the Nats’ last four games and was unavailable during Friday night’s 11-9 loss to the Marlins.

Chafin was going through a jogging drill in the outfield prior to today’s game, so the injury is not severe enough to prevent him from moderate physical activity right now.

The Nationals summoned Loutos from Rochester late Friday afternoon, then placed Chafin on the IL this morning. They were allowed to backdate the transaction only three days, to June 11, which was still three days after he suffered the injury. The soonest he could return would be June 26, but the team will be cautious with his recovery, not wanting to risk rushing him back and potentially making it worse.

NEW YORK – Before starting a three-game series against the Mets tonight, the Nationals answered a question that had been lingering since Sunday night: Who would fill the open roster spot?

After Sunday’s loss to the Rangers, the Nats optioned Nasim Nuñez to Triple-A Rochester, requiring a corresponding move when they arrived at Citi Field. The answer: Andrés Chaparro was officially recalled from Rochester in hopes he'll provide the Nats a much-needed right-handed boost.

“Very happy to be back in a major league clubhouse,” Chaparro said, via interpreter Mauricio Ortiz. “And it's also a lot of emotions because of what I went through last year with my baby. But again, happy to be back.”

What the 26-year-old and his family went through last year with his baby was an unbelievable tragedy. After his daughter, Gio Andrea, was born prematurely at the end of the season, she sadly passed away in late October.

That surely put his baseball life in the back seat. But Chaparro entered spring training with a good chance to make his first Opening Day roster, only to have that chance ripped away from him after a good camp when he injured an oblique muscle.

NEW YORK – After a 2-4 homestand, the Nationals are back on the road for a quick trip to Citi Field to play three games against the Mets. The Nats are actually a respectable 15-17 on the road this season. But they’re only 3-7 in away games against their National League East rivals.

The Nats have the right man on the mound for tonight’s opener as they try to get back to their winning ways. MacKenzie Gore has been nothing short of excellent to start this season, with a 2.87 ERA, 1.142 WHIP and major league-best 12.9 strikeouts per nine innings. The lefty has only been charged with a total of three runs over his last four starts, including back-to-back shutout performances over 13 innings against the Mariners and Cubs.

But perhaps more important for the Nationals is what they do against the guy who takes the mound for the other team. Griffin Canning has been impressive to start his first year in New York. The veteran right-hander is 6-2 with a 2.90 ERA and 1.322 WHIP over his 12 starts. And he’s coming off an impressive six shutout innings with seven strikeouts against the Dodgers his last time out.

The Nats did make a roster move this morning to help the offense: They officially recalled Andrés Chaparro from Triple-A to take the roster spot of Nasim Nuñez, who was optioned to Rochester after Sunday’s game.

But wait, the Nationals weren’t done. They also claimed right-hander Ryan Loutos off waivers from the Dodgers this afternoon and optioned him to Rochester, filling the 40-man roster.