New York Jets will be without Sam Darnold for Monday's NFL clash with the Cleveland Browns, with the quarterback suffering from glandular fever.

Jets coach Adam Gase confirmed Darnold's illness on Thursday, though there is not yet a timeline on his return.

Darnold missed Wednesday's training session, with Gase telling reporters the 22-year-old had been instructed to stay home.

The Jets' only other quarterback is Trevor Siemian, and Gase indicated Darnold could miss "multiple weeks", though a return on October 6 to face the Philadelphia Eagles could be possible considering the Jets have a bye in Week 4.

Darnold struggled through the team's Week 1 loss to the Buffalo Bills as he completed 28 of 41 passes for 175 yards and a touchdown.

Siemian, 27, has not seen action since 2017 when he was a member of the Denver Broncos.