Browns veteran linebacker Karlos Dansby doesn't need anyone to point out the surprising statistics about Cleveland's defense.

He knows there are holes — too many of them.

The Browns have the worst rushing defense in the league, dead last among 32 teams.

"This is the truth and the truth hurts," Dansby said. "No excuses."

Cleveland's defense is allowing 155.5 rushing yards per game and is on pace to have its worst run defense since 2000, when it gave up 156.6 per game. Back then, the Browns had a built-in excuse: they were in just the second year of their expansion era. But this year's defense, expected to be the team's backbone, is letting runners of all shapes and sizes run wild.

Shoddy tackling. Poor technique. Ineffective game plans. A new scheme. Young players. Injuries.

The Browns have been rattling off reasons for their inability to stop the run since the opener, when Pittsburgh's Le'Veon Bell rushed for 109 yards and a touchdown.

Bell is one of the NFL's best running backs. However, last week, Jacksonville was winless and had the league's worst rushing attack before rolling up 185 rushing yards on the Browns and getting their first win. Adding insult to injury, Jaguars running back Denard Robinson, a former Michigan quarterback filling in for injured starter Toby Gerhart, did most of the damage, gashing the Browns for 127 yards.

Browns coach Mike Pettine has spent each week doing his best to defend his team's porous defense.

"It's frustrating," said Pettine, a former defensive coordinator. "It's something we look at, but we don't want to panic about it. When it's a lot of little things, sometimes it takes some time to get that corrected."

This week, the Browns will be facing an Oakland team that comes to town with the league's worst rushing offense.

Stop me if you've heard this one before.

Part of Cleveland's problem has been a rash of injuries to its defensive line. Starters Phil Taylor (knee surgery), Ahtyba Rubin (ankle) and backup Billy Winn (quad) have all been sidelined with medical issues. The 6-foot-2, 325-pound Rubin, one of the team's best run stuffers, could be back this week.

Rubin would help, but the Browns' defensive problems seem deeper than personnel.

Even six games into the season, the defense is still struggling to learn nuances of Pettine's 3-4 system, which he brought over from Buffalo and is having Jim O'Neil run for him. Cleveland's defensive coordinator meets with the media once a week, and every week so far he's had to address the alarming rushing stats.

"I wish it was one thing and we could just get that one thing corrected," O'Neil said. "Unfortunately, it's not. I am confident that we are headed in the right direction. I have a lot of confidence in the coaching staff. I have a lot of confidence in the players that we're going to get it fixed. It's something we're addressing."

O'Neil has been talking to his players about being "one step faster," which can mean everything from defenders separating from offensive blockers more quickly to alignment to recognition before the ball gets snapped.

Dansby, an 11-year veteran, said the main issue has been a lack of discipline, leading to missed tackles and holes at the line that should be closed.

"Man, it's all about technique," said Dansby, who signed as a free agent in March. "If you don't play with great technique you're going to miss tackles, you're going to let guys squirt out, you're going to have big runs. It's evident when you watch the film. Guys don't get in their right gap, and boom, you're going to have a big run. The defense is predicated on you doing your part."

And, according to Bryant, listening.

"If we execute what the coaches ask us to do, then we'll stop the run 100 percent every play," he said.

If they don't, teams will keep piling up yards on the Browns.

NOTES: Pettine didn't divulge any changes to Cleveland's offensive line. RG John Greco filled in for injured Pro Bowl center Alex Mack last week at Jacksonville with Paul McQuistan taking Greco's spot. Pettine said the team has tried "different rotations" in practice. ... Winn was back on the field after being sidelined the past two weeks. ... Offensive coordinator Kyle Shanahan said he's not concerned about running backs getting into a rhythm. Shanahan said if Ben Tate, Terrance West or Isaiah Crowell want more carries "they need to separate themselves and show that they're obviously better than the other guy."