Jacob deGrom, who is dealing with a stiff neck, will have his start pushed to Saturday, with Matt Harvey starting in deGrom's place on Friday, reports Ken Rosenthal of Fox Sports.
Harvey will be pitching on regular rest since the Mets were off on Monday.
DeGrom has a 1.89 ERA and 0.84 WHIP with four walks and 22 strikeouts in 19.0 innings (three starts) this season.
Harvey has a 2.45 ERA and 0.98 WHIP with three walks and 15 strikeouts in 18 1/3 innings (three starts).
The Mets open a three-game series against the Nationals at Citi Field on Friday night at 7:10.