Pitcher Ryan Mattheus. (Associated Press)

Right-handed reliever Ryan Mattheus has made three appearances during his minor league rehab assignment, the latest coming Tuesday at Class AA Harrisburg. Mattheus, who has been on the disabled list since he broke his throwing hand punching a locker May 22, will need to make another four appearances before he returns, Manager Davey Johnson said.

The most pressing question is not when Mattheus returns, but how the Nationals react when he does. After early-season struggles, Johnson has set up roles in the bullpen in a way that allows for effectiveness. Mattheus has been solid, but his return may upset the balance.

“I don’t have to address that issue right now,” Johnson said. “A week or 10 days, no telling what might happen.”

Johnson is right, of course. The Nationals have the depth to trade a reliever from their bullpen – if there’s a team out there that wants to make Drew Storen a closer, for example, that might be best for both sides. And an injury could always strike and make Mattheus’s return more essential.

But if everything remains status quo, the Nationals will have a difficult choice when Mattheus returns. Their current bullpen contains no obvious candidates to be sent to the minors. Lefties Ian Krol and Fernando Abad began the year in the minors, but their addition helped fix the Nationals’ bullpen, Krol in electric fashion – he’s only 22, but he shouldn’t be going anywhere.

“The left side of the bullpen is really critical going forward,” Johnson said, answering a question about the Nationals’ second half in general.

Tyler Clippard and Rafael Soriano are obviously entrenched at the back end. Ross Ohlendorf is the Nationals’ only long reliever and he done a commendable job. Craig Stammen has options remaining, but he’s been a versatile and frequently dominant weapon.

Storen has an option remaining, too, and the 4.81 ERA he has compiled as Johnson juggled his role would seem to make him a possible odd man out. But he’s a pitcher who saved 43 games two years ago and is as talented as any reliever on the staff. He had a rollercoaster first half, but the Nationals are decisively a better team with him than without.

And so where does Mattheus fit in? He has an option, too, and so it’s possible Mattheus the one who’s left out when he comes back. But he, too, seems to be too good for minor league duty.

But as Johnson said, there’s still time for the Nationals to let the situation play out, and we know the problem of having too many pitchers never remains a problem for long.