LAKE FOREST, Ill. (AP) Despite their 0-3 start, the Chicago Bears believe they have the right formula on defense.

Special teams are where they are really struggling.

The Bears are so confident in their defensive progress that they dealt pass-rush specialist Jared Allen to the Carolina Panthers on Monday for a sixth-round draft pick, but the team's problems covering kickoffs and punts continue to perplex coach John Fox as the team prepares for Sunday's home game against Oakland.

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''It's no different than playing any kind of defense,'' Fox said. ''You've got to get off blocks. If they block everybody, it's usually not good.''

A week after Arizona's David Johnson returned the opening kickoff 108 yards untouched for a touchdown to start a Bears loss, Seattle's Tyler Lockett returned the opening kickoff of the second half 105 yards for a TD that broke open Sunday's tight contest with the Seahawks. The Bears also gave up a field goal in the first half after allowing a 64-yard punt return by Richard Sherman on a trick play.

''Any time you give up a kickoff for a touchdown, it's going to change momentum,'' kicker Robbie Gould said. ''In a tough place like Seattle, on the road, it's going to change that momentum. The defense played great - they kept us in the game for a long time, and then we gave up that play which obviously changed the momentum of the second half. We've just got to do a better job.''

Bears special teams have utilized numerous young players as the bottom of the roster constantly changes in a rebuilding year. Fox didn't want to use his players' inexperience with the system as an excuse.

''Our special teams, offense and defense are all new systems to these football players,'' Fox said. ''There were some pluses in that game. I thought our punt protection was pretty good. We did partially block two punts. So it wasn't all bad. I know it's got to be some kind of a record to go back-to-back games with kickoff returns for touchdowns. I'm not really proud of that. But hopefully guys that were on those teams, on that coverage teams, are looking and learning.''

Defensive players believe they have learned something about their 3-4 scheme.

The pass rush Sunday produced the first four Bears sacks, and none came from Allen. Although the trade of Allen surprised players, they felt they had achieved success for the future.

''Some of that dog started coming out,'' McPhee said. ''That's that fun part.''

McPhee saw the attitude change in the defense.

''You could see in some of them plays we were playing with an attitude,'' he said. ''We were playing with a swag, and all that goes to show that it's coming along. The defense is starting to play together.''

The Bears considered Allen expendable because they have McPhee, Lamarr Houston, Willie Young and Sam Acho at outside linebacker. Allen had 5.5 sacks last season but none this season.

NOTES: Nose tackle Jeremiah Ratliff can return this week to the lineup after a three-week suspension for a league substance abuse violation when he played with Dallas in 2013. However, the team isn't saying yet that he'll be back against Oakland. Ratliff suffered an ankle injury in preseason after the announcement about his suspension. ... The injury status of tackle Jermon Bushrod (concussion) and nose tackle Will Sutton (bicep) will be updated Wednesday.