David Goldman/AP

During his usual pregame chat, Nationals Manager Davey Johnson stated his preference for the starting rotation quite simply: Holding up his left-hand, he said, “I would like this against Philadelphia,” and then switching to the right hand, ”and this against St. Louis.”

With 12 games remaining and the Nationals’ magic number to clinch a National League East down to eight, Johnson is trying to maximize the matchups. St. Louis, a strong right-handed hitting team, hits left-handers well, and Philadelphia vice versa.

Tuesday’s rainout and Wednesday’s doubleheader prompted Johnson to schedule Chien-Ming Wang as a spot starter on Sunday to avoid making Jordan Zimmermann pitch on short rest. As a result, the starters behind Zimmermann in the rotation get an extra day of rest, which gives Johnson the opportunity to tinker.

“I’m matching up to get what I think is the best matchup and to get a little more rest,” Johnson said.

Zimmermann is scheduled to pitch Monday in the closing game of the series against the Milwaukee Brewers, a right-handed heavy lineup. Left-hander John Lannan will pitch the opening game against the Philadelphia Phillies on Tuesday.

Then, Johnson said he wanted to use his left-handers, Gio Gonzalez and Ross Detwiler, for the remaining games of the series against the Phillies, who are 21-25 against left-handers. While he didn’t give the specifics, here is a potential possibility: Detwiler started Thursday and could pitch Wednesday. Gonzalez is scheduled to pitch Saturday and could pitch on regular rest Thursday.

All of this would push Edwin Jackson, Friday’s starter, back to next Friday to start the opening game of a three-game series against St. Louis. He would be followed by Zimmermann and Lannan, thus giving the Nationals two right-handers against the Cardinals who are 52-53 against right-handers.