WASHINGTON -- The Nationals placed third baseman Anthony Rendon on the injured list prior to Tuesday night’s game against the Cardinals with a left elbow contusion, a move (retroactive to Saturday) that comes nearly 10 days after Rendon got hit in the elbow from an errant pitch from Marlins starter Jose Urena on April 20.

Rendon missed seven of the Nationals’ eight games after the injury, but he stayed off the injured list because the team remained optimistic his return to the lineup was imminent. Initially, they believed Rendon would be sidelined for only a few days and he felt good enough to play this past Friday night against the Padres. His elbow was swollen again the next day, however, and after waiting for an improvement the past few days, the Nats decided they could no longer continue playing with what was effectively a 24-man roster.

Left-hander Dan Jennings was promoted from Double-A Harrisburg to take Rendon’s place on the roster, and Austin Adams was designated for assignment to create room on the 40-man roster. Jennings was brought in for the ninth inning of Tuesday's 3-2 loss to the Cardinals, where he retired the first two batters he faced before giving up a single and a walk.

“[Rendon] wanted to play. He tried to play. It didn’t work out,” manager Dave Martinez said. “We thought he was getting a little better. But it got to a point where it was kind of a stalemate. So we had to make a decision.”

An MRI taken Saturday confirmed Rendon's injury is just a bone bruise and there is no fracture. The Nationals drained fluid from the elbow recently and the roster move should give time for the bruise to heal. Rendon had been attempting to swing before each game to see if he would be available to pinch-hit, but this should allow him a few days off from baseball activity.

The Nats are hopeful he will be ready to be activated May 7.

“I think as much as he wanted to play, he can ease his mind now and see if we can get this thing calmed down,” Martinez said. “And get him ready to come back and play and help us win.”

It leaves Washington without its best position player for at least a week.

And Rendon had been off to perhaps the best start of his career. Through 20 games, he compiled a slash line of .356/.442/.740 and 1.4 Wins Above Replacement, per Fangraphs, and had been in the midst of a career-best 17-game hitting streak before the injury.

Without Rendon, Howie Kendrick is expected to get most of the playing time at third base, but Martinez does not want to overtax his 35-year-old veteran, so Wilmer Difo, who is starting at third Tuesday, and Adrian Sanchez are likely to get some playing time as well.

But Rendon’s presence in the lineup will be missed, especially for a team trying to climb its way back after a slow start to the season. And Rendon also becomes the latest Nationals infielder sidelined, joining shortstop Trea Turner (index finger) and Ryan Zimmerman (foot) on the injured list.

“We just got to keep going, keep getting after it,” Martinez said. “And we’ll get these guys back.”

Jennings joins Nats from Double-A

Jennings takes a lot of pride in being ready to pitch every day. He has made at least 70 appearances in each of the past two seasons, and no reliever pitched in more big league games from 2017-18 than Jennings, who tied Andrew Chafin of the D-backs with 148 games.

That’s what the Nationals added to their bullpen on Tuesday night, a pitcher who might be able to lighten the workload on their ailing bullpen.

“That's something I took pride in,” Jennings said. “I’m always ready every day. Managers that had me in the past knew they never had to ask because I wasn't going to shy away from taking the ball and they basically have to rip it out of my hand once I am out there. I love to pitch ... I can't even fathom a 'day off.'”

Jennings, who signed a Minor League deal with Washington on April 13 after he was cut by the Angels out of Spring Training, made three appearances at Double-A Harrisburg before getting this callup.

Nats make annual visit to Walter Reed Center

The Nationals made their annual visit to the Walter Reed National Military Medical Center in Bethesda, Md., on Tuesday afternoon, a chance for players, coaches, broadcasters and team officials to spend time and chat with veterans and military families throughout the facility.

The Nats visited some inpatient rooms, chatted with veterans working on physical therapy in the Military Advanced Training Center and joined a contingent of military families at the USO Warrior and Family center for lunch.

“It was emotional,” Martinez said. “You get to appreciate what life really means. You’re talking to some really young people who go out there and sacrifice their lives for us. You talk to them and you’re sharing stories and you see a different perspective. And it put things into perspective for most of us. I love talking to them. You watch them and what they’re going through, but they’re very positive. And they were all willing to go back and do it again.”