Florham Park, N.J. — Sam Darnold is back at the New York Jets facility, feeling healthier by the day.

Patience and caution are the two key plays in his game plan right now, but the second-year quarterback is looking forward to when he can get back under center.

That could come as soon as Week 5 at Philadelphia on Oct. 6 — which would easily beat the doom-and-gloom predictions that Darnold could be out much longer.

"I have full confidence I'll be ready for the Eagles game," Darnold said Wednesday. "But I'm not going to promise anything. That's the goal the doctors have set, and that's the goal I've set for the game to be back for."

And, really, he can't at this point. It's all up to how his body responds and continues to heal from a bout with mononucleosis.

He met with reporters for the first time since being diagnosed last week and looked a bit tired but mostly healthy. Darnold said during a radio interview Tuesday with 98.7 ESPN New York that he has only lost 2 pounds from the illness by making sure he continued to eat even when he didn't feel up to it.

The 22-year-old quarterback returned to the team facility Tuesday and tried to find a silver lining in being sidelined after going 28 of 41 for 175 yards and a TD in the season-opening loss to Buffalo.

"Continue to learn the offense, but at the same time, hoping to come back and come back stronger than I was," he said Wednesday. "That first game, I wasn't myself. I wasn't playing like myself. I felt a little more uncomfortable than I had been in preseason and in training camp.

"So, just looking to come back strong, come back knowing the offense that much more and playing well."

The key to him being cleared for physical activity is making sure his enlarged spleen, a key symptom of mononucleosis, shrinks back to normal size.

"This is something that is serious," coach Adam Gase said. "If his spleen bursts, we've got a problem."

For now, the Jets are in a quarterback carousel, with Luke Falk next up to start — giving New York three starting quarterbacks in three games. That's because Trevor Siemian, who injured ligaments in his left ankle during the second quarter of the Jets' 23-3 loss to Cleveland on Monday night, was placed on injured reserve. He needs surgery and is out for the season.

So, Falk will start for the first time in his second NFL season. And, that's after he was merely a practice squad player a week ago.

After replacing Siemian against the Browns, Falk went 20 of 25 for 198 yards in his NFL debut.

New York also signed David Fales on Wednesday to back up Falk. The 28-year-old Fales, in his fifth NFL season, played under coach Adam Gase in 2015 with Chicago and the last two years in Miami. He was with Detroit in training camp and waived before this season.

A sixth-round pick by the Bears in 2014 out of San Jose State, Fales has thrown for 287 yards and one touchdown with an interception in three NFL games.

"With the situation we're in, we needed someone that could come in here and if something happened can go in the game and knows the system to where it doesn't become like five plays against New England," Gase said. "That would be fun. So, we needed someone that could come in, he's really familiar with the system, he's really smart, he's been in it three years now. He's somebody that I've played in a game before, I kind of know how he operates. It's a good fit for us."

Falk and Fales are just placeholders, of course, until Darnold is fully healthy and can come back.

Darnold said the plan is for doctors to check his vitals on Monday to see if he can be cleared to start getting some running in, and then go from there. The Jets have a bye-week break and don't play again until the game against the Eagles.

For now, though, Darnold was just thrilled to be in meetings, watching on the practice field and kidding around with his teammates again.

"One guy said it's like looking at a ghost because you haven't been here in so long," Darnold said with a big smile. "In all seriousness, it's really good to be back. I missed those guys."

• LB C.J. Mosley (groin), WR Demaryius Thomas (hamstring), DL Quinnen Williams (ankle), LB Jordan Jenkins (calf), WR Josh Bellamy (shoulder) and RB Trenton Cannon (ankle) all sat out practice. ... LT Kelvin Beachum (ankle), NT Steve McLendon (hip), S Rontez Miles (hip) and RG Brian Winters (shoulder) were all limited.