If having a laid-back backup quarterback is worth anything, the Jets will be in good hands with Trevor Siemian at the offense's controls while Sam Darnold is recovering from his bout of mono.

What's his most important task for Monday night's national-TV game against the Browns?

"Do my job, run a clean operation, and get the ball in the end zone," Siemian said with no nerves audibly jangling. "It's pretty simple."

And is there anything he can take from his 24 starts as the Broncos' QB in 2016 and '17?

"I don't know what I can take from that ... the sense that I've been there and done it a little bit," he said, thoughtfully but again not anxiously. "It's been a while. I'm chomping at the bit to compete and be out there with the guys. I'll just say I feel comfortable."

Jets coach Adam Gase noted that comfortability when he broke the news at today's news conference that the Darnold diagnosis came in at 10:15 Wednesday night and that he could miss several weeks, and how the team responded to that news.

"I told them this morning in the team meeting, talked about how our next-man philosophy does not waver," Gase said. "It's about everybody doing their job. That's why Trevor is here. We signed Trevor specifically because of his 24 starts in his career with a winning record, he has a lot of experience, has been on winning ballclubs, has the respect of the locker room. The reaction I got, the way that guys looked, was, 'Let's go,' and there is confidence there."

Gase expanded on his reasons for liking Siemian's game, dating to his days as Miami's head coach.

"I feel like there were so many crossover games we had with somebody playing Denver where I saw a lot of his games and his time when he was starting," Gase said. "We worked him out when he was coming out but he had that ACL and he couldn't really move. When Denver took him and he became the starter after Peyton [Manning] left, I kept seeing him play a lot and in my head I kept saying, 'Wow, this guy really throws a nice ball. He gets it out and it comes out clean.'

"It just seemed like the more film I watched on him and then when we started evaluating him, then I really liked him."

Siemian said nothing much in the playbook is changing with the QB rotation.

"We've been running the same scheme, the same plays. I feel pretty comfortable with what we're doing," he said. "I'm excited to compete for sure."

And he said part of the reason for that excitement is the group of teammates he's going into battle with on Monday and the following Sunday at New England.

"I'm not worried. We've got such a mentally tough team, so many good players. These guys are built for this," he said. "I know Sam's not hurt, but we're going to have a couple of injuries this year. This team's built to handle it."

And one of those players, center Ryan Kalil, echoed his new QB's and his coach's remarks.

"I feel bad for Sam. I know how frustrated he is, talking to him yesterday. So I think it's smart, giving him time to get better. I know he's pretty sick. So next man up," Kalil said. "It's a physical game. You have to stay ready no matter what. And I think we have great guys in this locker room with great attitudes. And I thought practice went really well today."

Statistics won't tell a lot about an offense being run by Darnold and one being directed by Siemian. But one set of metrics suggest that the Jets offense for the short term won't look drastically different. Here are the two QBs' key drive numbers, Darnold from his 14 Jets starts and Siemian (who didn't play at Minnesota last year) in his two years running Denver's offense:

But as Siemian said, his and the Broncos' past is not as important as his and the Jets' now:

"There's nothing I did two years ago that's going to help me at tomorrow's practice or on Monday night. Like I said, I'm real excited to compete."