CLEVELAND — There's only so much you can know about a team at the beginning of the season, particularly one with a new coordinator.

And after a 21-18 loss to the Browns on Sunday, they were frustrated at their ability to adapt.

When the Panthers arrived in Cleveland ready to face the Browns, the top passing offense in the league (heading into Week 3) knew they were squaring off against a new defensive coordinator for Cleveland, one who played at the fourth-highest rate of man coverage in the league, 41.5 percent of the time; the group played even above that in Week 2, showing man coverage 62.9 percent of the time.

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That was a defense they largely prepared for. But Cleveland ruled out their top corner, Tyson Campbell, from Sunday's game, which changed their typical scheme, and had one huge goal in the passing game: keep offensive rookie of the year Tetairoa McMillan covered up as much as possible.

"They were down Tyson Campbell, one of their starting corners, so it's like I'm naturally thinking, 'OK, they might want to try to play like a little bit more zone than they want to,'" said veteran tight end Darren Waller, explaining how the Browns switched up their defense as they got into the game. And unfortunately for the Panthers, their focus became McMillan.

"So it's like we're seeing more of their two-high coverage than we would have wanted to in situations where it's like, OK, these may be certain play-action shots we're trying to take to (TMac). And they pressure with those two high looks. So it's like they were playing a chess match too, showing things that we didn't see early on from them."

In the end, McMillan was held to two catches on five targets for 17 yards in the loss,

The first thing did not directly cause the second. But it was a solid game plan that contributed to the Browns' win and the Panthers' loss.

"They covered us pretty closely," explained coach Dave Canales after the loss, of the Browns focusing on McMillan. "They mixed some man in some zone; they did a good job that way, and ultimately we had one-on-one opportunities. We didn't hit a lot of them, you know, really until BT (Brycen Tremayne) kind of hit that go-ball down towards the end."

The pressure Waller mentioned meant quarterback Bryce Young was pressured on 51 percent of his dropbacks, forcing him to get rid of the ball quickly.

"Some of the times we're trying to go to (TMac), it's like they got pressure, they rotated the coverage in a new way that we hadn't seen on tape before," continued Waller. "So those are the kind of things that happen early on in the season, and you got to (take) hats off to them defensively.

Making matters more difficult, the Panthers lost receiver Jalen Coker just after halftime to a quad injury. Without his presence to pull the defense away from McMillan, it was easy to lock in on one guy with a zone scheme that kept him bracketed.

"I think they probably heard everybody talking about them playing man, and I'm sure that they were the ones leading that narrative," noted receiver John Metchie III. "So, just making a lot of things look like man early on and dropping out of it, whether they were getting into their cover two and stuff. It was a lot of that at the beginning of the game, on 3rd downs. But just normal downs, making a lot of things look like man matchups and just dropping out of it, maybe to try and throw a switch up, you know."

With Coker and Xavier Legette out (ruled inactive before the game with a knee injury), and McMillan drawing tons of attention, the Panthers turned to guys like Tremayne, who finished as the leading receiver with four receptions for 83 yards, Waller, who had five catches for 51 yards, and Metchie, who caught the day's only touchdown.

But the Panthers have been very transparent that their offense runs through McMillan. Without the ability to scheme or throw him open more, so many things stalled.

"First off, there's some stuff that I can definitely do better. Obviously (TMac's) a special player, he's a huge part of this offense," said Young after the loss.

"Wasn't able to end the way that we want in any capacity, but again, haven't watched the film yet; we'll go back, watch it. I'll take accountability for us not getting it done and things not going smoothly, and then we'll grow from it.

Added Canales, "That's something, as coaches, we got to look at and make sure we're putting him in better positions to be able to be effective for us. We want him to be a big part of what we're doing."