By Dan Durkin-

CHARLOTTE, N.C. (CBS) — You have to go back a long way to find the last time the Bears have scored a touchdown in the second half of a game. Since scoring on their first drive of the third quarter against the Jets in Week 3, the Bears have gone 16 drives and nearly six full quarters of football without a second-half touchdown.

Those are inexcusable numbers for a team built to win games with its offense.

Undoubtedly, every phase lent a hand in the Bears’ 31-24 loss to the Panthers on Sunday, but the offense has to be counted on to play four quarters of football if this team wants to be considered as anything other than ordinary.

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The Bears are now 2-3 on the season and have lost back-to-back games to 2013 NFC playoff teams, falling under .500 for the first time in the Marc Trestman era.

“From our standpoint, I’ve got to take accountability for our failure to get it done in the second half,” Trestman said. “We didn’t get it done in all three phases, and that starts with me.”

As they did last week against the Packers, the Bears’ offense had a deflating end to the first half.

Leading 21-7, they had a golden opportunity for a touchdown on a screen pass to Matt Forte, but tight end Martellus Bennett didn’t make a block on safety Roman Harper. That missed block ended up being a huge swing in the game. The drive stalled afterward, and Robbie Gould pushed a 35-yard field goal attempt wide right. The Panthers then flew 75 yards down the field in under two minutes to narrow the gap to 21-14.

Coming out of that drive with no points seemed to have a carryover affect on the rest of the game, as for the second straight week, the Bears’ offense didn’t run a single second-half play in their opponent’s red zone.

Crucial second-half turnovers by franchise players derailed any chance of winning. Nursing a 24-21 lead with six minutes remaining, the offense had a chance to put the game away. Instead, it went into self-destruct mode, turning the ball over on consecutive plays.

First it was quarterback Jay Cutler, who sailed a pass over the middle of the field that was intercepted. Four plays later, the Panthers kicked a field goal to tie the game. Then Forte fumbled, which the Panthers converted into the game-winning touchdown.

Two plays within two minutes of each other, and the Panthers turned them into 10 points to steal the game away from the Bears. Frustration is mounting within the locker room.

“It is frustrating early on, because it is not like we are getting beat, we are beating ourselves,” Forte said. “If we can get out of our own way, we can win some games.”

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.