WASHINGTON -- Trevor Rosenthal, currently on the injured list due to a viral infection, is headed to the Nationals’ complex in West Palm Beach, Fla., where he will work on the mechanical adjustments he has tinkered with all season and maybe work his way back into a late-innings relief role.

“Just [to] be able to pitch consistently,” Rosenthal said as he packed up his locker prior to Monday night’s 6-3 loss to the Cardinals. “Here, I haven’t been able to do that, and I feel like that’s exactly what I need.”

Rosenthal’s first season in D.C. -- and his return to the mound since missing all of 2018 after undergoing Tommy John surgery -- has been a nightmare on the field. In seven appearances, he has allowed 12 runs on seven hits and nine walks while recording just nine outs. Rosenthal has uncorked five wild pitches and hit three batters.

During the team’s most recent road trip, Rosenthal dropped about 10 pounds with a viral infection, so the Nationals want him to take some time to regain the weight and work on his mechanics before he is activated. Nats manager Dave Martinez hesitated to put any timetable on his return, but Rosenthal said he does not expect it to be a long process. He will begin a program to get him back to throwing every other day until he progresses to a point where he can face hitters in West Palm Beach.

“I think, talking with everybody, the general consensus is it’s not going to take long,” Rosenthal said. “It’s just a matter of getting it rolling, getting a little confidence and bringing that confidence here.”

The Nationals signed Rosenthal to a one-year $7 million contract on Nov. 3 with the hope that he could recapture his past form when he was a closer and key bullpen arm with St. Louis for six seasons. His fastball velocity has remained steady, averaging 98.1 mph with his four-seamer, but his command has been missing all season. So the Nats want to give Rosenthal an opportunity to iron out any adjustments and regain his confidence before they put him back in their big league bullpen.

“I hope that we could use him in the back end of the bullpen still,” Martinez said. “That's why we got him. Track record indicates that's who he is.”

MRI confirms elbow contusion for Rendon

Anthony Rendon is out of the Nationals' lineup Monday night against the Cardinals, his seventh absence in eight games. Rendon received an MRI on his left elbow Sunday, which confirmed the contusion initially diagnosed by the team last week. But the Nats still stopped short of placing him on the injured list, hoping the gradual improvements he has made in recent days mean his return to the lineup is coming soon.

“He says it'll be sooner than later,” Martinez said. “When you miss a guy like Anthony in the lineup, hopefully he wakes up tomorrow and the swelling's better and we get him going.”

Rendon got hit on the elbow by an errant pitch from Jose Urena on April 20 in Miami and missed the next four games. He returned to the lineup Friday night and played the entire game, but his elbow swelled back up the following day. Martinez has been optimistic Rendon will be available to pinch-hit late in the games, but his elbow bothers him when he extends it to swing.

“If he can't play for the next few days, then we'll consider putting him on the IL,” Martinez said.

To provide some help on the bench in Rendon’s absence, the Nationals promoted infielder Adrian Sanchez from Double-A Harrisburg and optioned Erick Fedde back to Harrisburg.

Zimmerman provides injury update

Ryan Zimmerman said he has been battling plantar fasciitis in his right foot for a “couple weeks,” but he aggravated the injury leaping for a ball at first base in Wednesday’s game against the Rockies. He attempted to play through it at first, but it quickly became apparent the injury was not rebounding as quickly as he wanted.

“We realized for five months we weren't going to be able to do this,” Zimmerman said. “So, take some time off, get it right and hopefully we think we caught it early enough where it won't take that long. This first week will be critical to see how it feels and kind of go from there.”

Zimmerman did not think this foot injury was as severe as his battle with plantar fasciitis in his left foot in 2015, when he missed seven months.

“I think that one, if I remember correctly, was torn pretty good,” he said. “I don't remember the exact percentage or anything like that, but I don't think this one is as bad as that one was. But that doesn't mean anything. We just have to see how this first week goes and from there we'll develop a plan.”