The Washington Post’s Dan Steinberg, LaVar Arrington, Mike Wise and Jonathan Forsythe discuss debate the Nationals’ growing rivalry with the Phillies. (Post Sports Live)

The Washington Nationals are in an enviable position this spring: They have few unknowns. The lineup is complete. The starting rotation has been set since December. Players are entrenched at every position, save for a catcher returning from knee injury. Even the bench figures to be the same.

Then, there’s Henry Rodriguez.

Of all the known commodities on this team, Rodriguez is the enigma. The flame-throwing right-handed reliever can be extreme at either end of the spectrum, otherworldly stuff or mind-boggling wildness.

Over the past month since players reported, the exact composition of the group with the most turnover from last season, the bullpen, has come into clearer focus. The Nationals expect to break camp with a bullpen that contains one left-hander and a lot of right-handers, and they believe Rodriguez, flaws and all, is a part of that. They think he can be better now that the elbow pain that long bothered him is gone thanks to surgery. They know that if the 26-year-old doesn’t make the team out of camp they lose him.

“I’m not going to lose a good talent,” Nationals Manager Davey Johnson said. “In ’11, he showed he had the stuff to close and was a backup closer for [Drew] Storen, and was a primary one last year. He’s obviously not someone I’m overlooking. He’s one of my favorites.”

When the Nationals signed veteran closer Rafael Soriano in mid-January, the framework of the bullpen was all but set. Soriano moved late-inning relievers Tyler Clippard and Storen, both closers in the past, up an inning. Because Clippard and Ryan Mattheus are effective against left-handed batters, the Nationals believe they can rely on Zach Duke as the lone left-handed reliever. And barring any injuries, Craig Stammen and Rodriguez would round out the remaining spots.

Part of the Nationals’ reasoning for sticking with Rodriguez is that he is out of minor league options. If he can rebound well from his surgery, the Nationals believe he still has the potential to throw 100 mph with command like he did last spring. Before he melted down on the mound last summer, he began the season as the closer because of injuries to Storen and others, and successfully converted his first five save chances.

Months removed from his August surgery and back on the mound this spring, Rodriguez admitted that his throwing elbow has hurt for more than a year and a half, maybe two. He brushed it off at first as the normal soreness and pain in a pitcher’s arm after a taxing appearance.

But the pain got progressively worse with time. Rodriguez would ice his elbow and arm like most pitchers do after games. Even when he slept, he felt the twinges in his right elbow. “As long as I didn’t pitch, it didn’t hurt,” said Rodriguez, who also spent time on the disabled list last season with a sore back and finger injury.

Finally late last summer, he told the Nationals about the pain. On Aug. 31, Rodriguez had surgery to clean up a bone spur and arthritis in his right elbow. He already had spats of inconsistency but the injury, the Nationals believed, put his up-and-down season in context. Rodriguez, however, isn’t sure how much the elbow pain affected him because he had already been dealing with the discomfort for a while.

“I couldn’t tell you because I knew it’s something I’ve had for a while,” he said in his most extensive comments about the injury since surgery. “I couldn’t tell you if it ended up affecting me. I don’t know.”

Rodriguez took the diagnosis of the source of his pain and timing hard. He wanted to play down the stretch and in the playoffs with his teammates. He rehabbed quietly in the mornings at Nationals Park. He didn’t pick up a ball again until November. Over the winter, he spent time with his wife and children in his native Santa Barbara, Venezuela. He lifted, ran and threw.

The discomfort in his elbow, Rodriguez said, is gone. He encountered a brief setback when he felt some arm tightness when he threw during spring training. The Nationals went slow with him and finally inserted him into a game on Friday. He fired 97 mph fastballs with ease, using only eight pitches to get three outs against the St. Louis Cardinals. “I feel like new,” he said.

His wife and children were in the stands at Space Coast Stadium when he pitched for the first time since surgery. The following morning, he bounced around the clubhouse with a broad grin across his face.

“I’ve seen him calmer and in talking to him, he tells me he’s happy and at peace, and that’s most important for him,” said catcher Wilson Ramos, a fellow Venezuelan. “He has to keep his mind relaxed and do his job.”

Rodriguez pitched again on Monday, notching two quick outs before giving up a single and hitting a batter. Johnson yanked him from the game because the Nationals want to keep him on a low pitch count for now until he is soon placed on a regular workload.

Rodriguez thinks only about what lies in front of him. His time away from pitching in games, he said, helped him get a better sense of his delivery and body. His goals for next season are to stay healthy and help the Nationals win. He isn’t worried about his future if he struggles.

“I don’t have to prove anything to anybody,” he said. “I just have to feel healthy. And being healthy, the rest will take care of itself. The work will speak for itself.”