Mets ace Max Scherzer left Saturday’s game early after just 67 pitches with “left side fatigue” during the Mets’ 7-1 loss to the Nationals on Saturday night at Citi Field.

Scherzer entered into the Mets dugout after pitching for five innings with his head down. The 38-year-old starter had allowed just earned one run against one of his former teams.

Jeremy Hefner, a Mets pitching coach, trailed behind him into the tunnel.

The three-time Cy Young winner dealt with an oblique injury in May and returned in early July.

Scherzer has a 2.27 ERA in 122 2/3 total innings pitched this season.