CLEVELAND — When Panthers head coach Dave Canales was breaking down Sunday's 21-18 loss to the Browns, he said, among other things, "we've got to be smarter."

The man in the middle of the game's pivotal play agreed with him.

The lead changed hands four times in the fourth quarter, but the final one was the killer for the Panthers.

It appeared that cornerback Akayleb Evans had intercepted a pass to end a Browns threat, but back near the line of scrimmage, a flag was lying on the ground.

Linebacker Bobby Okereke was called for roughing the passer after hitting quarterback Deshaun Watson as he let the ball go, giving Watson another chance.

Watson may have sold the call, but he left the field for one play, returned for the next, and a play later found tight end Harold Fannin for the game-winning score.

"Just chasing after the quarterback, obviously he was outside of the pocket, so just trying to get in his throwing lane, was focusing on making sure my momentum wasn't carrying forward so I wouldn't get a roughing in that situation," Okereke said. "Bang-bang call, tough play, but I've got to be smarter in that situation."

That was one of six times Okereke said a version of "need to be smarter" during a three-minute interview, but it was the kind of mistake the Panthers couldn't afford in a game played in such small margins.

"In real time I thought I was clean," Okereke said. "And then obviously when I saw the flag just, ... unfortunate call for the team. I've just got to be smarter in that situation.

"I was focusing on making sure my momentum wasn't carried through to hit him in the head or neck area, but I've just got to be smarter in that situation, not leave it up to the refs."

Of course, it wasn't just one play, but it was indicative of the day for the Panthers.

The offense was sluggish for most of the first three quarters. They struggled to protect quarterback Bryce Young, and they didn't run the ball until late.

And there were dropped interceptions prior to that one, one by Lathan Ransom and one by Will Lee, the kind of missed opportunities that will haunt them.

That penalty was crushing. But it was one of many.

"All right, game of execution," Canales began his post-game with. "That's what it comes down to: a couple of red zone and fringe opportunities, came away with field goals and not touchdowns, big difference there. Missed a few turnover opps early on on the defensive side and gave them an opportunity to continue their drives, some untimely penalties, some things that really hurt us, and we've got to be smarter in some of those areas. Got to contain the rush better; Deshaun was able to get out a couple of times, and we know the challenge of it, but we got to be disciplined with our rush and be able to do that.

"I mean those are the margins, and that's what happens."​

When asked about the Okereke penalty, Canales said it was unfortunate, but it can't happen.

"I saw him get hit in the head by somebody's hands; I don't know who that was, but we can't do that," Canales said. "We have to go lower on the quarterback when the ball's in the air; you have to make that decision right at the end to either put your hands on the quarterback or not, and we made the wrong decision in that case and extended the drive. And then he was able to create a little bit of extra time on the scramble play, which is something that he can do well, and so, we can do a better job there as well."

Again, it wasn't just one play. For an entire half, the Panthers didn't look like themselves.

They entered the game first in the league in passing offense (312.5 yards per game), second in scoring (35.5 points per game), and fourth in total yards (409.0).

But in the first half, their best offensive plays were roughing-the-passer penalties against the Browns.

Other than a 30-yard catch-and-run by Chuba Hubbard — who was held to 18 yards on 10 carries — and a 17-yarder to Tommy Tremble, the Panthers didn't have a play longer than 13 yards.

They managed just 113 yards in the first half, and just 18 yards on 10 carries by Hubbard.

That left them settling for field goals, and seeming fortunate to get those.

"We didn't handle the movement well up front, and we're looking at it schematically and structurally the runs looked fine; we missed some blocks up front," Canales said. "We knew the challenge of this group is that they're quick; they move at the point they do different things, and we didn't handle that well early. Finally, we were able to kind of settle in towards the end of the game, and really the feature of that touchdown drive was the run game, the play actions, the offense that we know. The Browns did a great job covering us, making it challenging. Some of their rush patterns creating a little bit of pressure for Bryce, so he had to get the ball out a little bit earlier than he needed to."

So many of those things seemed to have been solved when Young and the offense finally got their footing in the fourth quarter, when his touchdown to John Metchie III gave them a 18-13 lead.

But then came the penalty, that big, obvious mistake in a day when the margin was small enough that any could have been decisive.