Milone was placed on the 10-day disabled list Wednesday with a sprained left knee, Mike Puma of the New York Post reports.
It's unclear when Milone sustained the injury, though it could have been during his last start; he lasted just 1.1 innings and was clobbered for eight runs (seven earned). It's also unclear how long the 30-year-old will be sidelined with the issue, though a timetable should become clearer as the Mets release more on his status. Travis d'Arnaud was activated from the disabled list in a corresponding move.