Darnold, 22, hasn't played since the Jets' Week 1 loss to the Buffalo Bills on Sept. 8. The team announced Darnold's diagnosis Sept. 12, saying the starting quarterback could miss multiple weeks. Darnold missed Week 2 and Week 3, before the Jets had a Week 4 bye. He said he is practicing this week as though he will be the starter for the Jets' Week 5 game against the Philadelphia Eagles.
Darnold is being cautious upon his return. The Jets gunslinger has an enlarged spleen as a result of the mononucleosis. A hit could cause a rupture to the spleen, resulting in a potentially fatal injury. Darnold has been wearing a protective brace to protect the spleen at practice. He plans to wear the brace if he is cleared to play in Week 5. He won't be cleared to play if his spleen remains enlarged.
"It's a tough thing because you want to stay safe," Darnold told reporters. "I want to make sure that I'm safe out there and I'm not going to die.
"For me, sitting back and watching the team play and not having anything to do about the win or the loss is not a good feeling for me."
The final call on Darnold's status will be made Friday, after he has an ultrasound and blood test. Darnold took the majority of the Jets' first-team reps at Thursday's practice.
"Constantly, we're checking with him like how are you feeling? Are you tired? What's your conditioning like? We keep talking to him," Jets coach Adam Gase said. "We keep watching him. You can tell when a guy gets really exhausted to a point where throws would look different, drops would look different, you would see a fatigue if there was one and we didn't see that."
Jets backup quarterback Luke Falk completed 68.1 percent of his throws for 296 yards and an interception in two appearances in relief of Darnold. Falk has yet to throw a touchdown pass and has been sacked seven times.
"Football is a crazy game," Darnold said. "But at the same time, I want to make sure that I'm safe first and foremost. That's the doctor's mindset. The doctor wants to make sure that I'm as safe as can be out there and risk of injury for me is just as high as anyone else and just as low as anyone else.
"I'm going to be cautious, but at the same time, I'm going to play just like I would if nothing happened."
Darnold completed 28 of 41 passes for 175 yards and a touchdown in Week 1. The No. 3 overall pick in the 2018 NFL Draft completed 57.7 percent of his throws for 2,865 yards, 17 touchdowns and 15 interceptions during his rookie campaign. Darnold missed three games in 2018 due to a sprained foot.
The Jets face the Philadelphia Eagles at 1 p.m. EDT Sunday at Lincoln Financial Field in Philadelphia.