WASHINGTON -- While nothing has been discussed between him and the front office, Nationals manager Davey Johnson is already thinking about when right-hander Stephen Strasburg will pitch his first big league game of the season.

Strasburg, who allowed five runs in 1 2/3 innings for Class A Hagerstown on Wednesday, most likely will replace right-hander Jordan Zimmermann in the rotation, but the Nationals are being cautious when it comes to Strasburg, who is coming off Tommy John surgery. No date has been set for Strasburg's season debut.

Zimmermann has 15 more innings until he reaches his limit for the season. Johnson is still not sure how he will handle Zimmermann's final innings.

Johnson said he needs to talk to general manager Mike Rizzo and head athletic trainer Lee Kuntz before any decision is made regarding Strasburg's season debut.

For example, if Zimmermann pitches seven innings against the Reds on Thursday and five more in his next start, it would mean he would have three more innings left. Johnson is still wondering if it's worth Zimmermann making another start if that occurs. Another scenario is for Zimmermann to pitch five innings per start.

"I was kind of interested in the math -- looking at Jordan Zimmermann's innings to date," Johnson said. "It looked like to me he would have three more starts."

Desmond back at leadoff for Nationals

WASHINGTON -- Nationals manager Davey Johnson is already in auditioning mode. On Wednesday, he decided to give shortstop Ian Desmond another chance at the leadoff spot against the Reds.

Johnson is looking for someone in the organization to be a table-setter for next year in case the Nationals are unable to acquire one in the offseason.

Desmond started the season at the leadoff spot, but wasn't productive, going 9-for-50 [.180]. However, Johnson feels that Desmond has the ability to bunt and run a little better than Rick Ankiel and Danny Espinosa at the top spot.

Ankiel, who has been the leadoff hitter for several weeks, was put in the second spot of the order, while Espinosa went from second to the sixth.

"It's not perfect," Johnson said. "[Desmond] really thinks of himself as a one or two hitter. He can run, bunt, sparkplug type. ... One thought was to hit [Desmond] second and have [Espinosa] leadoff, but knowing [Espinosa] is real successful hitting down in the order, he liked it."

Desmond will not be the leadoff hitter for Washington the rest of the way. Once he is called up, infielder Steve Lombardozzi will get a shot at the leadoff spot. Lombardozzi is having a productive season, hitting .317 with Double-A Harrisburg and Triple-A Syracuse with 78 runs scored and a .366 on-base percentage.

Lombardozzi more than likely will get starts at third base, second and shortstop.

Worth noting

Nationals catcher Ivan Rodriguez, on the disabled list because of a right oblique strain, was seen playing catch on Wednesday without any problems. Manager Davey Johnson is hoping that Rodriguez is activated from the disabled list by the time the team expands its roster in September.