Mike Pettine didn't mince words with his players, coaches and reporters about the Browns' defensive performance Sunday.

Asked if he was concerned by the number of yards -- 469 on 314 passing and 155 rushing -- Cleveland surrendered in Sunday's 27-20 loss to the Raiders, Pettine said "very," as he detailed what he described as a "wasted opportunity" in front of a FirstEnergy Stadium crowd that was "begging for something to cheer about."

"In the NFL, you have to be consistent," Pettine said. "You can't have the highs and the lows. You have to play well throughout a game."

The Browns defense had its spurts of the kind of play that was common throughout last week's win over the Tennessee Titans.

The unit held tough near the goal line on an impressive, game-opening drive by Oakland and limited the Raiders to a field goal. It showed some resiliency in the fourth quarter after Travis Benjamin's fumbled punt return, giving the offense one last shot at a comeback with an essential three-and-out.

In between, though, there was just too much inconsistency for Pettine's liking, and Oakland's offense pounced with both its running and passing game. All of the Raiders' scoring drives spanned at least 70 yards.

"We have to tackle better," cornerback Joe Haden said. "We have to get off the field on third downs. Myself included, everybody, we just have to be way more consistent on defense. We have flashes where we do really good. Then, we have flashes when we don't play like ourselves. We just have to do it full force."

For a second time in three weeks, that inconsistency struck at the end of the first half.

Trailing 10-3 with less than 2 minutes to play, the Browns defense surrendered 70 yards on just five plays and saw Oakland take a two-touchdown lead after Derek Carr's touchdown pass to Seth Roberts.

"It's very frustrating," defensive lineman John Hughes III said. "It's something we've got to work on in practice and get corrected."

After Cleveland drew within 10 following Gary Barnidge's touchdown catch near the end of the third quarter, the Raiders marched right back down the field -- aided largely by a 55-yard reception by fullback Marcel Reece that was littered with missed tackles -- to go back on top by 17 early in the fourth.

During the second half, the Browns offense had just one possession -- its last -- when it trailed by a single score.

"It was mental mistakes," rookie defensive lineman Danny Shelton said. "We didn't rally together. Those are just Day 1 things."

After Week 3, the Browns defense knows it can be better and knows it has to play that way as soon as next Sunday, when it travels to San Diego.

Efforts like Week 2's against the Titans, when Cleveland registered seven sacks and forced three turnovers, are fresh in the players' memories. The Browns didn't sack Carr on Sunday and forced one turnover, a fourth-quarter Amari Cooper fumble forced by Christian Kirksey and Haden.

The secondary, which Pettine considers to be the backbone of his defense, knows what it's capable of accomplishing after a 2014 season in which it finished first in a number of statistical categories. A game like Sunday's hurt for every member of Cleveland's defensive backfield.

Step 1 toward reigniting those positive feelings of Week 2 starts with learning from a performance like Sunday's.

"We just aren't playing good football," veteran defensive back Tramon Williams said. "We played well last week but we have to be more consistent. That's about it."