WASHINGTON ---- Jason Bay’s return to the Mets lineup will have to wait at least until the Subway Series: The outfielder was scratched from Thursday’s lineup against the Nationals because of flu-like symptoms.

Scott Hairston took Bay’s place in left field. Bay was activated from the disabled list on Wednesday after missing six weeks with a rib fracture, but did not play because manager Terry Collins wanted to give him an extra day of rest. Bay has been battling flu-like symptoms in recent days.

Kirk Nieuwenhuis is slated for center field against the Nationals and Lucas Duda will play right. Hairston entered Thursday’s action with seven hits in his previous 14 at-bats and was second on the team in home runs with eight.

The Mets had concerns earlier Thursday when Omar Quintanilla reported to the ballpark with a sore left index finger, but the shortstop was cleared to play. Otherwise, the Mets would have been forced to use Jordany Valdespin at shortstop.

mpuma@nypost.com