Quarterback Sam Darnold has been medically cleared to return to games by the winless Jets and will start on Sunday against the Dallas Cowboys, the team announced on Tuesday.

Darnold had missed the Jets’ last three games and the team’s bye week after he was found to have mononucleosis. He took part in practices last week but was only cleared for full contact after having further tests Tuesday morning.

The Jets (0-4) have been ineffectual in his absence and are off to their worst start since 2003. Behind Luke Falk, the third starting quarterback the team has used this season, the offense only mustered 495 total yards and two offensive touchdowns in three games without Darnold.

The Jets currently rank last in the N.F.L. in offense (179.5 yards per game) and passing yards (113.5).