(Julio Cortez/AP)

Storen, who saved 43 games last year, returned to Washington on Thursday for an MRI on his right elbow. The test revealed inflammation in his joint but no structural damage to the ulnar collateral ligament. Doctors prescribed rest.

Johnson called Storen’s throwing program “very conservative,” with the Nationals intent not to rush him back in order to pitch by opening day.

“This time of year, you take it extremely slow,” Johnson said. “He needs to be 100 percent ready. … I’m going to prepare for the possibility that he doesn’t break with us. I’m not saying it’s out of the question. But I’m going to prepare my staff for the possibility Storen might not be my closer for those games.”

(Julio Cortez/AP)

“It’s hard to replace what he does,” Johnson said. “You want to avoid weakening two positions.”

In Lidge and Rodriguez, the Nationals have disparate options to fill in for Storen. The Nationals signed Lidge, 35, late this winter as a free agent after he spent four seasons with Philadelphia. He has 223 career saves, and in 2008 he recorded the final out of the World Series. After returning from shoulder surgery last year, he relied heavily on his slider as his fastball velocity dropped to 89.3 miles per hour on average, down from 93.6 in 2009.

The Nationals acquired Rodriguez, 25, last winter in a trade from Oakland. Rodriguez threw the hardest fastball in the majors last year, according to FanGraphs.com. Once he began finding the strike zone with it, he became a weapon in the back end of the bullpen. Rodriguez saved two of the Nationals’ final seven games last year.

This spring, Lidge has struck out has seven and issued no walks in five scoreless innings. Lidge contended with injuries during his previous three spring trainings, but he entered this season fully healthy and has yet to experience any setbacks.

“I’m feeling real good right now,” Lidge said last week. “To be honest, it’s kind of come around a little bit quicker than I thought it would, which is obviously great. My arm strength is kind of going the right way. I’ve been able to get out there and use both the four-seam and two-seam fastballs.

“I’m feeling very good about being healthy and being able to go through the progression I want to in spring training. It’s just real nice to be out there and not worry if my arm is hurting, but work on things to get ready for the season.”

Last season, Lidge returned in late July after he underwent shoulder surgery during spring training. In his first outings, he threw his fastball around 87 and 88 miles per hour. By the time the season ended, he had upped his velocity to 91 and 92. After his smooth spring, Lidge anticipates throwing with the same power he reached at the end of 2011 once this season starts.

“There’s nothing prohibiting me from throwing inside or outside, throwing sliders wherever,” Lidge said. “I was a little tentative when I came back last year. The way I finished off the year last year, command-wise, I feel like I’m there right now. … If I’m throwing 90 with command of slider, that’s good. Anything about that is gravy.”

Rodriguez has been dominant this spring, picking up where he left off last season. In six scoreless innings, Rodriguez has allowed one hit and two walks while striking out five.

If Storen misses extended time, it would open the door for the Nationals to add another reliever, most likely Ryan Mattheus or veteran Chad Durbin. Mattheus served a valuable role last season, posting a 2.81 ERA in 32 innings, and Johnson trusts him. Durbin, though, signed a minor league deal with an opt-out clause, meaning he could leave the Nationals if they do not put him on their major league roster.