UPDATED 1:52 p.m.

CORTLAND, N.Y. -- The Jets roster lined up along one sideline, ordered to run dreaded gassers. They sprinted the width of the field twice, and repeated about 10 times, before the double whistle signaled the end.

This was Rex Ryan's punishment when a second straight training-camp practice went beyond competitive, and became combative.

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"Being physical is one thing," the Jets coach said today. "Going past that is something else. That’s what I didn’t like. That’s why we stopped, and we had to remind guys that enemy is not in green and white."

It was the same message Ryan delivered after practice yesterday, when a melee of about 20 players erupted on the sideline after post-play extracurricular activity between running back Joe McKnight and safety D'Anton Lynn, the son of McKnight's position coach.

Evidently, the message didn't get through the first time. So Ryan stopped practice twice today.

He first stepped in when he saw rookie running back Terrance Ganaway try to run through linebacker Demario Davis in what he called a "thud" period, when players are instructed to simply thud off of each other. A skirmish began, and Ryan quickly stepped in, scolding his team.

"That’s not what you are looking for; that’s not being physical," Ryan said. "That to me is being selfish. And so I told the guys about it and sure enough, apparently someone never got the message."

That someone was cornerback Antonio Cromartie. Later in practice, during passing drills, Cromartie jawed at Stephen Hill after holding the rookie receiver. Ryan had issued a warning to his team, dangling the gassers as punishment, and the following play proved to be the final straw.

Cromartie, a seven-year veteran, delivered what Ryan considered an inappropriate hit on tight end Dustin Keller.

"I thought 'Cro' should have backed off and not hit Dustin," Ryan said. "He's trying to be physical and pick his play up. We always talk about developing habits. But in that situation, that’s your teammate. You don’t want to do it. I thought 'Cro' was wrong in that situation."

Cromartie declined to speak to reporters today, loudly expressing his disdain for the media when approached by a member of the team's public relations staff.

The practice field became stunningly quiet as the players retreated to the sideline for the gassers. When the sprints were complete -- Tim Tebow, for what it's worth, out-ran all his teammates -- Ryan huddled his team at midfield.

He urged his players to be smart, to play physical but yet protect each other. When Ryan was done with his speech, quarterback Mark Sanchez stepped in to echo Ryan's message.

It was the first time Ryan, entering his fourth season as the Jets head coach, has ordered his team to run gassers.

"I just wanted them to know how serious I am about it," Ryan said. "And I also wanted to run them until I was tired."

Ryan has resolved not to lose "the pulse" of the team this year, as he admitted happened in 2011, and to stay on top of any potential tension in his locker room. But he bristled at the reference to last year, and said he's always tried to be in control and create a positive culture as the Jets head coach.

The past aside, that was certainly what Ryan did on the practice field today.

"I know what my job is. My job is to get this team ready to go," Ryan said. "And be the team that I envisioned having. We are going to, and that’s it."

Many of Ryan's players said his message got through loud and clear.

"I don’t know if we disappointed him, but we aren’t practicing the way we should be right now," safety Eric Smith said. "Go be physical but stop on the whistle."

Davis called it "great coaching."

"Whatever he says, goes," Davis said. "We’ll always be loyal to him, and whatever he says, we’re going to always respond to it. (If ) he wants the extra (hitting) to stop, and he wants us to focus on playing, that’s what we'll do."

Ryan said after the gassers, the team practiced "exactly how I wanted them to practice." He clearly dislikes the public perception -- fair or not -- that his team is undisciplined and prone to chemistry issues.

"Everybody has a right to their opinion, there is no question about that. No matter how wrong they are," Ryan said. "I think we are a little more disciplined than what the general perception is out there or what have you. You can't have the wins that we've had in the past and not be a disciplined football team. It hasn’t been good enough, and we haven't won the Super Bowl yet, but certainly we’re able to."

The Jets' first preseason game is Friday, so they'll have a chance to hit another team then. Until then, Ryan left no uncertainty about what he expects in practice.

"I bet we don’t have (a fight) tomorrow," Smith said with a smile.

Jenny Vrentas: jvrentas@starledger.com; twitter.com/JennyVrentas