For most of this season, Morgan has been atop the lineup, but he is having a tough year. In the last two weeks, Espinosa has been at the top spot, but he may be better suited to hit lower in the order.
The Nats could also try to get a leadoff hitter via trade or free agency.
"The players will make the decision, whether it's Morgan, Espinosa, Bernadina, whoever," Riggleman said. "Somebody has to hit up there, and the one that doesn't will hit in the two spot. It's almost interchangeable.
"I think Nyjer can be a real plus for us in that two spot, but that means Desmond doesn't hit in the two spot, Bernadina [and Espinosa don't hit there, either]. It's going to have to work itself out at the end of the year and Spring Training."