Quarterback Carson Palmer takes part in some 7-on-7 drills Tuesday in the Cardinals' first 2015 OTA.

Carson Palmer heard the good-natured catcalls from his defensive teammates during the first organized team activity of the offseason Tuesday, not unexpected as the players finally got to match up offense against defense for the first time.

That was OK with Palmer. "They took one on the chin today," Palmer said with only a hint of a smile.

Not that Palmer, still rehabbing from his torn left ACL, got to take part in all the fun. He remains limited to individual and 7-on-7 work, he and the Cardinals playing smart with a 35-year-old quarterback whose health remains the most important factor in 2015 success.

But Palmer's time to return is coming quickly. He has been driven in his comeback in a way he could not have predicted, with a

mindset curated the day his knee was surgically repaired in mid-November – six months and two days ago Monday, Palmer noted in detail.

"He knows the clock's ticking," coach Bruce Arians said. "It is for a lot of guys on this team. You get a window to make a run and most of it depends on your quarterback. Right now, it's our window. There is a sense of urgency."

Palmer's urgency began on those difficult Sundays lying in his bed after he got hurt, his leg bandaged and in a CPM (continuous passive motion) machine while watching his teammates play games he should have been playing.

Once he had his surgery, "I just had a very tight focus, a very small vision, a certain intensity, a certain realness."

The focus comes across in his diligence about his diet, in his weekend stretching away from the facility, how he strength trains, in his playbook and film study. It isn't as if Palmer was a slacker before. He worked in the offseason. He even went through an ACL rehab once before.

Yet Palmer admitted that ticking clock has made a difference to him – even if he didn't quite understand that at first.

"I thought I was this way five years ago," Palmer said. "Now I am here and I realize I only have a couple of opportunities left and I was not this way. I was not this intense about everything.

"You only get so many opportunities and if you are lucky enough to play as long as I have, you don't know until you get to the end how small that window is, how few opportunities you will have. So I thought I was all-in and 100 percent in and very focused and committed and I was not compared to where I am now. It wasn't for lack of trying, it's just that I didn't realize it. I wasn't mature enough to realize it back then. (The end) wasn't as close to reality as it is now."

Palmer said he only got about 12 real plays Monday and that wasn't enough for him, which is why he is politicking the trainers and physical therapists so he can do more. Arians acknowledged there is a chance he could put Palmer into 11-on-11 work by minicamp, but he is being cautious, and why wouldn't he be? The Cardinals know that however much trust they might have in backup Drew Stanton, it's Palmer that keeps that window propped open.

The official all-clear for Palmer is still two months away, which remains good news given that training camp doesn't start for 11 weeks. In the meantime, Palmer works his way in slowly and gets mental reps by helping teammates – "He's coaching them up and that's what I love about him," Arians said – as his knee heals.

Rehab is important, Palmer said, but playing the game to prepare for the game, that's more important. That's where that focus becomes a sliver, and why getting on the field against a defense drives him.

"It felt good to be around humans, with that competition, that speed," Palmer said. "I have a lot of work to do."