(Manuel Balce Ceneta/AP)

As the Nationals wait until their first-round opponent is determined to finalize their NLDS rotation, they have not ruled out making John Lannan their fourth starter in the event they face the Atlanta Braves.

When Davey Johnson said the Nationals’ opponent would determine his Division Series rotation, the only pressing question seemed to be whether Ross Detwiler or Edwin Jackson would be the first to pitch after Gio Gonzalez and Jordan Zimmermann. But because of Lannan’s success against the Braves and Atlanta’s trouble with left-handers, the Nationals are still considering Lannan.

“Yeah,” Johnson said before largely deflecting the question. “You’re asking questions that don’t need to be answered yet. We don’t even know who we’re playing, and it could be two series later. I’ll address that when it’s time to address it.”

Johnson wants to build his rotation based on the opponent, and the Braves feature a heavily left-handed lineup that includes Michael Bourn, Jason Heyward and Freddie Freeman. Against left-handed starters this year, the Braves have gone 30-31, 17th in the majors. Against right-handers, they are 63-37, best in the majors.

Lannan also has a history of success against the Braves. This year, he allowed them two runs over seven dazzling innings in one start. In his career, he has a 3.20 ERA in 98 1/3 innings against the Braves.

That being the case, Jackson has been a steady force in the Nationals’ rotation all year. He can veer to extremes, and in his last start in St. Louis he recorded four outs in a shelling, but he’s also the only Nationals starter with playoff experience. He was also quite good against the Braves this year, striking out 16 and walking three in 12 1/3 innings while allowing four earned runs.

Jackson seems to have the edge, but it’s something worth considering. And if Jackson throws a second straight clunker today to end the season, then that’ll be worth factoring in, too.