WASHINGTON — Matt Harvey’s magic number is two.

The Mets right-hander could make two more starts in the regular season, according to general manager Sandy Alderson, as the team attempts to walk the tightrope between overusing and under-using the pitcher before he potentially appears in the playoffs.

Alderson outlined a plan Wednesday in which Harvey would start against the Yankees in the Subway Series that begins at Citi Field on Sept. 18 and again in the final series of the regular season, which begins two weeks later against the Nationals.

Logan Verrett is scheduled to take Harvey’s spot in the rotation on Monday against the Marlins.

Harvey, who tied a career high by allowing seven earned runs in the Mets’ 8-7 victory over the Nationals on Tuesday, faces a cutoff slightly above 180 innings for the regular season. Alderson said he is still discussing various scenarios with Harvey’s agent, Scott Boras, and surgeon, Dr. James Andrews.

Harvey, in his first season back from Tommy John surgery, has logged 171 2/3 innings.

As much as there is concern about Harvey pitching too much before the postseason, the same holds true of the pitcher being underused.

“That is something Dr. Andrews has always wanted to avoid, which is on the one hand fatigue from overuse and on the other hand loss of continuity and rhythm from under-use, so that’s the balance,” Alderson said before the Mets faced the Nationals.

The Mets, according to Alderson, have not discussed any plan for how Harvey would be used in the postseason.