A new defensive scheme that was supposed to transform a struggling unit has led to perhaps the least productive defense Raiders history.

The Raiders (1-3) returned to practice Monday after having four days off for their bye week looking for answers on how to fix a defense that is on pace to allow the most points and yards in a season in team history.

They will be tested right out of their bye, with a cross-country trip to Atlanta (5-0) on tap to face Matt Ryan and an offense that has scored touchdowns on the highest percentage of drives in the league so far.

“I’m definitely surprised,” defensive back Michael Huff said of the struggles. “I was the one buying in, believed in the scheme, believed in the coaches, believed in everything. I’m not staying away from that. Watching on film, we see what we can be. We’re still one play here, one play there. It’s there to be had. We just got to make the plays.”

Huff was the most vocal proponent of the new scheme, saying he was looking forward to playing a “real defense” for a change under head coach Dennis Allen and new coordinator Jason Tarver.

Until his death a year ago Monday, longtime Raiders owner Al Davis was heavily involved in the team’s defense, picking coordinators who would usually use his preferred system of bump-and-run coverage on the outside and pressure coming from a four-man defensive line.

Allen, the former defensive coordinator in Denver, became the team’s first defensive-minded head coach since John Madden in the 1970s. He brought in a defense that featured multiple fronts and coverages and was supposed to have more blitzes than Oakland was used to using.

That new variety hasn’t led to new success so far as the Raiders have allowed 125 points in the first four games — the most at this point of the season since 1962. Oakland is giving up 411.5 yards per game, allowing opponents to complete 71.5 percent of their passes and has managed just three sacks and three turnovers in four games.

“We got to have 11 people flying around to the football, flying around like their hair is on fire,” Allen said. “That’s the way you play defensive football.”

Part of the problem can be attributed to injuries to starting cornerbacks Ron Bartell and Shawntae Spencer. Bartell went out with a broken shoulder blade in the season opener against San Diego and Spencer sprained his right foot the following week in a loss to Miami.

Bartell will be out until at least Nov. 11 and Spencer remains in a walking boot and has not been cleared to practice.