When the Nationals were National League East bottom-feeders, Lannan was at the top of the rotation and made 122 starts from 2008-11. But he was the odd man out this spring, and has gone 4-1 with a 4.13 ERA in six spot-starts.
Lannan has pitched well when called upon -- particularly against the Braves -- which is why Johnson is leaving the door open in case the Nats open the Division Series with Atlanta.
"We don't even know who we're playing," Johnson cautioned Wednesday. "And it could be two series later. I'll address it when it's time to address it."
Lannan's first big league start of the year came against Atlanta in the second game of a July 21 doubleheader. Atlanta had won the first game and was closing in on the Nats in the standings before Lannan scattered two runs on five hits over seven innings.
Jackson, who started the season finale on Wednesday in Washington, came in 1-2 with a 7.92 ERA since the beginning of September. Detwiler is 2-2 with a 3.73 ERA in that span but has given up eight runs in his last two starts (both losses), spanning 7 1/3 innings.