Washington Nationals manager Davey Johnson says Stephen Strasburg has "probably" two or three starts remaining before the ace pitcher is shut down for the season.

Johnson said Thursday he delivered the news to Strasburg on the plane ride home from Wednesday's win over the Miami Marlins.

Johnson says he has a "pretty firm plan" for Strasburg, but it's based on how many innings the right-hander pitches in his next starts.

Strasburg is 15-6 and has thrown 150 1/3 innings. The Nationals have not announced the innings limit they've imposed on him in his first full season since undergoing Tommy John surgery.

Barring a rainout or other change in the rotation, Strasburg's final start appears set for either Sept. 7 vs. Miami or Sept. 12 at the New York Mets.