CHARLOTTE – If you've already watched enough of Matt Kalil to make up your mind about the left tackle, you might see this as a puff piece. But if you're willing to have an open mind, perhaps you'll see more.

"What everybody seems to forget is Matt had major surgery," head coach Ron Rivera reminded this week. "He didn't have a normal offseason [last year]. He didn't have a normal training camp."

Call those excuses, but that doesn't make them invalid.

Hip surgery is no joke. That's what Kalil underwent in September 2016 to fix an issue that began bothering him in high school. The pain sharpened his third season in Minnesota, and his only recourse two years later was to go under the knife.

"I've had knee scopes here and there, but I never had a major surgery like that," Kalil said. "So I thought it was just, 'OK, the problem's fixed, now I'll be good and it won't hurt.'"

And it didn't anymore. But as surgery corrected one problem, it created others.

The longer muscles function a certain way, the longer it takes them to adjust to change. Kalil's bad hip had limited his bend for about 10 years. So when surgery fixed the hip – where so much of the body's anatomy is connected – the muscles around it needed time to learn a new range of motion.

"I was struggling in OTAs because I couldn't really move that well yet," he said. "My groin was having issues because of the new mobility. Probably midway in camp is when I started feeling [better]."

For a guy whose athleticism made him a No. 4 overall pick, struggling to move was a significant problem. It didn't help that it took him a bit to learn a new system.

"Obviously, you saw during the season the first few games I was kind of just iffy and a little behind," Kalil admitted.

Added Rivera: "Early on he was stiff."

According to Pro Football Focus, Kalil allowed 4.0 sacks in the first three weeks of his first season in Carolina. But while sacks aren't the only relevant measurement for a pass blocker – and rarely do we know whose assignment was whose on any given play – Kalil gave up just 3.5 sacks over his final 14 games, including the Wild Card visit to New Orleans.

On the ground, the Panthers had much more success running outside left tackle than they had in 2016. In rushing attempts that spanned from the left hash to the left sideline, Carolina jumped from 18th to 5th in rushing yards per attempt and from 20th to 2nd in rushing first downs.

"As the season progressed, you began to see the improvement; you began to see [Kalil's] play trend up," Rivera said. "Now being healthy, having a healthy offseason has been good for him. So I'm excited about who he can be for us."

That healthy offseason is vital because last spring Kalil had to spend most of his time in the training room. Now he's graduated to the weight room for squats, power cleans, etc. You know, things offensive linemen need to be doing that Kalil wasn't able to do a year ago.

"I used to have to do what I could to survive. Now it's to the point where physically nothing's holding me back," Kalil said. "So I have a chance to excel and work on the things I want to work on rather than doing maintenance 24/7 and just trying to survive out there.

"I would say the point where I'm starting off now to last season is not even close. You can't compare the two. It's the difference between actually working out and training or rehabbing. Just from a strength standpoint, I feel night and day the difference."

Again, I get it. Many of you have made up your minds on Kalil. But he's the Panthers' left tackle. May as well give him a chance to prove he and Rivera are right about season No. 2.

"It takes a while to get back into it. That's one thing I learned because I had never been through anything like that," Kalil said. "You have so much stuff you have to worry about: calls, what the defense is doing, what my technique is, and on top of that, you have to worry about how I have to move so my body doesn't hurt.