Danny Espinosa, left, and Ian Desmond, right, are being entrusted to fill the major weakness — the Nos. 1 and 2 spots in the batting order — on a team that looks like it has no other holes. (Toni L. Sandys/The Washington Post)

Day after day this spring training, Davey Johnson wrote Ian Desmond’s and Danny Espinosa’s names at the top of the Washington Nationals’ lineup card. In case that had not been a strong enough message, Johnson sat them down last week. “This isn’t an audition,” the manager assured them. “You guys are my 1 and 2.”

Johnson had handed his two young middle infielders what might be the Nationals’ most crucial problem to solve. They have assembled a deep starting rotation, a shutdown bullpen, an athletic defense and a powerful middle of the order. But at the top of their lineup, the Nationals are simply counting on the maturation of Desmond and Espinosa to counteract the issue that, more than anything else, has caused them to rank 25th of 30 major league teams in runs scored the past two years combined. The hitters at the top of the lineup, simply, have not reached base enough.

Nationals leadoff hitters have reached base at a dismal.292 clip over the past two seasons, the worst in the majors and 13 points clear of the San Francisco Giants, the next-worst National League team. And the Nationals’ on-base percentage actually got worse from 2010 to 2011, dropping from .300 to .285 — the worst on-base percentage for any major league team’s leadoff hitters in a single season since 2002 and better than only eight since 1980.

Nationals No. 2 hitters last year compounded the problem with a .283 on-base percentage, third lowest in the majors. With so many outs made by their first two hitters, the Nationals could not create chances for their best hitters to drive in runs.

Last year, as he primarily hit third, Ryan Zimmerman came to the plate with runners on base in 41.1 percent of his plate appearances. On average, hitters across the National League — batting anywhere in the lineup — batted with a runner on base 43.9 percent of the time. Essentially, the Nationals turned Zimmerman into their rally starter.

They will attempt to change that with Desmond and Espinosa. Desmond said he does not sit and ponder the specific areas he wants to improve. When asked, though, two objectives came to mind first. “I’d like to strike out less,” he said. “I’d like to get on base more.”

Desmond began last season as the Nationals’ leadoff hitter, but after an early slump then-manager Jim Riggleman dropped him in the lineup before April ended. By the all-star break, Desmond had a .269 on-base percentage, making him one of the least productive offensive players in the majors to that point.

Desmond, though, experienced an offensive revival that coincided with Johnson slotting him into the leadoff spot. After Johnson moved him back to the first spot on Aug. 17, Desmond hit .305 in his final 41 games.

“After the second half I put together, as bad as I struggled for the first half, to be able to bounce back like that, I could have easily just shut it down,” Desmond said. “To fight through that and salvage the year, that’s what a big leaguer does.”

The Nationals may also look for help at the top of their order from another source. For Tuesday’s2-0 spring training loss to the New York Mets, with Ryan Zimmerman staying back in Viera, Fla., Johnson scribbled Steve Lombardozzi into the leadoff spot with Desmond hitting second behind him. And then Johnson said Lombardozzi would likely hit leadoff on days he starts for the Nationals, should he make the team.

“Well, that’s where he usually hits,” Johnson said. “He’s having a remarkable spring.”

Lombardozzi, 23, has handled every situation this spring like a veteran. He has gone 10 for 30 with two walks while bouncing around the infield, which has put him in strong position to make the Nationals’ opening day roster. If the Nationals summon Lombardozzi to the majors, Johnson would aim to get him at least 300 at-bats over the course of the season in order to not stunt his development.

Tuesday, Johnson revealed a means beyond resting Espinosa, Desmond or Zimmerman to get Lombardozzi his required at-bats. In the likely event Lombardozzi makes the Nationals’ roster, Johnson would consider playing him in center field. Johnson did not want to brand Lombardozzi a utility player, but he compared Lombardozzi to versatile Tampa Bay Rays star Ben Zobrist, who typically cobbles together the at-bats of a regular while toggling between as many as five positions.

How is all of this is relevant to the Nationals’ need for a leadoff hitter who can clog the bases for the middle of the Nationals’ order? In 2,001 total minor league plate appearances, Lombardozzi compiled a .369 on-base percentage.

Especially in the National League, when the pitcher frequently tries to bunt runners into scoring position, Johnson prefers top-of-the-order hitters with the capacity to hit for power.

“It’s a luxury if you can have 1 and 2 that can drive in runs,” Johnson said. “A lot of times a guy can get on, but he has a hard time driving somebody in. I may sacrifice a little bit of on-base percentage, but through the course of the game they’ll be in situations where we bunt a guy over, and we’ve got a run producer up. As much as I look at on-base percentage, I also look at guys who can produce runs.”

It would be enough, and a substantial improvement, if the hitters at the top of the Nationals’ lineup simply let others produce the runs.