During an interview aired Thursday on ESPN's "Pardon The Interruption," Johnson indicated that Strasburg could be limited to 160 innings and claimed that the first-place Nationals would not jeopardize the All-Star's future.
The Nationals have maintained throughout the season that they would limit Strasburg's innings this season, regardless of their position in the standings.
Nationals general manager Mike Rizzo previously had stated that there was "no magic number" for the innings limit, claiming that he alone would decide when Strasburg's season will end.
Johnson mentioned 160 innings during the interview in reference to Washington's plan last season for Jordan Zimmermann, who was shut down after throwing 161 1/3 innings.
"One of my rules of managing is I try to do what's best today with an eye on tomorrow," Johnson said. "What's best for Strasburg is looking ahead in his future. And if all the reports that I get is the best thing we can do is after 160 innings shut him down -- that's what we did with Jordan Zimmerman last year, although we were in third place.
"(It's) a little different this year. But you do what's best for the player, not only for today but for the long haul."
Strasburg, 24, has pitched 121 1/3 innings over 21 starts this season for the Nationals, who entered Thursday with a 2½-game lead atop the National League East. The former No. 1 overall draft pick has anchored Washington's rotation this season, going 11-5 with a 3.12 ERA and a league-leading 154 strikeouts.
Strasburg underwent Tommy John surgery on his elbow toward the end of his rookie season in 2010. The right-hander managed to return toward the end of last season and pitched in only 44 combined innings that included minor-league rehabilitation outings.