Jose Reyes has a Grade 1 intercostal strain and has been sent to the hospital to be examined by a doctor, Mets manager Terry Collins said late Tuesday.
Collins said Reyes suffered the injury during a swing in Game 1 of Tuesday's doubleheader.
He is expected to be out of the lineup for 2-3 days.
Wilmer Flores played third base in Game 2 of the doubleheader in place of Reyes.
Reyes is hitting .239 with a .278 OBP and .493 SLG with three home runs and eight RBI in 67 at-bats over 16 games with the Mets this season.