“Right now, I was more concerned in having somebody who can pick up Zim if his shoulder starts bothering him or something,” Johnson said. “In case he dove for a ball or something, who do I have to play there?”

Steve Lombardozzi could play third base, but as he plays regularly in left field, a new position, Johnson does not want to shift him around the diamond.

Johnson said Zimmerman, who missed two weeks with inflammation in his right shoulder joint, is healthy. He made clear that wanting DeRosa as a reserve third baseman was not a sign of concern. “He’s so valuable in the field, and any at-bat he could start off and feel real good,” Johnson said.

But Zimmerman’s 5-for-46 slump has left him at .222/.290/.310 for the season. His 65 OPS+ ranks 157th out of 163 qualifying players, right between Robert Andino and Brendan Ryan. Still trying to find a rhythm with a shoulder that is not 100 percent, Zimmerman has not yet been himself.

As the Nationals stretched today, Johnson lowered to one knee and gave Zimmerman a brief lesson. He mimicked a swing and explained an adjustment. Zimmerman nodded and smiled.

In Johnson’s mind, DeRosa will offer insurance for Zimmerman, not an alternative. Johnson is eager for his return. DeRosa has been out since April 28 with a strained left oblique. He has also dealt with the death of his father following a harrowing bout with cancer.

“He left me an e-mail and said that he was feeling great,” Johnson said. “He wanted to know what the plan was. And I said, well, the plan was for you to get some at-bats, start feeling real good and let me know when you’re feeling real good. And his answer was, ‘I’m feeling great.’ So I know he’s going to be playing tonight. And we’ll take it one day at a time. He could be here tomorrow or another 2-3 days. We’ll see.”