The New York Jets are coming off of a disappointing performance in Week 1. They held a 16-0 lead over the Buffalo Bills but then surrendered 17 unanswered points and lost a game they had complete control over.

For Week 2, they were to headline Monday Night Football in their matchup against the—also disappointing and winless—Cleveland Browns. Both teams had made massive changes to their rosters during the offseason and are led by second-year quarterbacks.

News broke today that one of those quarterbacks will not be participating this primetime matchup.

Adam Gase told reporters during his press conference before practice today that their starting QB, Sam Darnold would miss the game due to a sickness he had picked up.

The disease Darnold has contracted is mononucleosis. The team says he will be out indefinitely.

New York has a bye in Week 4, the earliest the Jets are targeting to get Darnold back is Week 5.