Sam Darnold is out for the Jets' game Monday night against the Browns because of mononucleosis, but the quarterback has told the team he's "already feeling better" and is hoping for a best-case scenario of a Week 5 return, according to team sources.

That return date is optimistic, but Jets coach Adam Gase noted this past week that it was a good thing that New York has a Week 4 bye.

Gase would not say whether Darnold has a good chance of being back for Week 5, but sources tell ESPN that the Jets are hopeful he can play against the Eagles that week or the Cowboys in Week 6.

Darnold's progress during the next week will be a barometer. He is expected to undergo another scan to determine whether his spleen is stable, the most concerning risk with the mono diagnosis, according to sources.

The second-year quarterback has been receiving the Jets' daily practice installs -- uploaded to his team-issued video device -- and is doing preliminary study on future opposing defenses like the Eagles and Cowboys, according to sources.

Darnold has been quarantined in his apartment, frustrated with his predicament, but he has some company with family members who have joined him.