Sam Darnold is Still Quarantined and Out Until at Least Week 5
By Sean Facey

The New York Jets will have to wait until at least Week 5 to get their young quarterback back out on the field.
Sam Darnold, who was diagnosed with mono prior to the team's Week 2 matchup against the Browns, is reportedly feeling better, but still remains in quarantine. He will have more scans on his spleen to monitor his condition next week.
Jets QB Sam Darnold is "already feeling better" and even though he remains quarantined with mono, a week 5 return vs the Eagles or week 6 vs. the Eagles has not been ruled out. He will have more scans the next week to monitor his spleen, per sources.
— Chris Mortensen (@mortreport) September 15, 2019
Even though they don't want to run the risk of other players in the locker room getting infected from Darnold, the Jets could certainly use him back as soon as possible. Without him, they have to start an extremely less appealing quarterback in Trevor Siemian.
Darnold has shown promise ever since he was drafted third overall in 2018. After finishing with 2,865 yards and 17 touchdowns in 13 starts last year, he kicked off his 2019 campaign with a respectable 175 yards and a touchdown to boot.
#Jets coach Adam Gase tells reporters that QB Sam Darnold will miss Monday’s game with mono. That is unexpected.
— Ian Rapoport (@RapSheet) September 12, 2019
The offense might have sputtered late against the Bills in Week 1, ultimately leading to the loss, but it's practically a no-brainer that the Jets are far better off when Darnold is under center.
For now, though, it's a waiting game. There's nothing they can do except sit back, monitor his condition, and hope that he'll at least be ready sometime in the near future.