Darnold has been diagnosed with mononucleosis and will not play in Monday's game against the Browns, Brian Costello of the New York Post reports.
Darnold missed Wednesday's practice with what was originally believed to be strep throat, but further testing has revealed that the second-year quarterback is suffering from mono. The timetable for a return is fairly unpredictable, as not only is Darnold likely suffering from extreme exhaustion, but head coach Adam Gase has said that he has already lost a considerable amount of weight. Consider Darnold week-to-week for now, but in his absence, Trevor Siemian will take over as the team's starter under center.