LAKE FOREST, Ill. — The Chicago Bears have looked lost on both sides of the ball most of this season and, after their 34-17 defeat in Detroit on Thanksgiving, it appears the season itself is nearly lost.

Nothing seems to add up for the Bears as they move the ball well at times yet fail to score, or dominate teams with their defense for a few series before issuing invitations to the end zone.

Now only mathematics keep Bears’ playoff hopes alive with a quarter of the season remaining and a 5-7 record after Calvin Johnson made 11 catches for 146 yards and two touchdowns, and the Lions exploded offensively following two straight games without a touchdown.

“Really frustrating,” running back Matt Forte said after rushing just five times for 6 yards. “It’s just frustrating because as a team, the talent we have on our team, we definitely are underachieving.

“A few guys have to do some soul searching for the rest of the season and plan how they want to play the rest of these games.”

Quarterback Jay Cutler, who threw two more interceptions, doubts the Bears will become quitters even if the only playoff chances are unrealistic.

“I think with the guys we have and character and integrity of the guys, I don’t think anybody’s going to quit,” Cutler said. “I think the coaches won’t let us, they’re not going to quit on us. I think the leaders of the team will make sure that we finish this right.”

Defensive end Jared Allen found another way to look at it.

“You play every game for what it is,” Allen said. “Misery loves company, right? You try to take everybody down with you. You play because it’s your job. You play because this is what we love to do.

“You go out there, and if you’re willing to shut it down, you’re willing to get embarrassed, I don’t want you on my team. And I don’t think we have one guy (like that) in there.”

The surprising aspect of this one was that the Bears actually started fast, ending a scoreless first-quarter streak of six games with 14 first-quarter points. They did it without any real practices in a short work week made it all the more surprising.

“We had a fast start, which was good,” coach Marc Trestman said. “We couldn’t sustain offensively. They did a good job defensively.

“We made the stops early and then they got on a roll and really made their money throwing the football and moving it around.”

Then a couple of holding penalties slowed the offense, the defense gave up touchdowns on three straight Detroit possessions and the entire game had turned. Matt Stafford went on to throw for a season-best 390 yards and the 21 second-quarter points Chicago allowed brought their season second-quarter deficit to 145-61.

So why does a team with playoff aspirations at the beginning of the season turn into a group of underachievers?

“Many things,” was Forte’s explanation. “I could stand here all day and talk about it.

“But I’m not going to point the finger or anything like that. There are a thousand things you could talk about, penalties, all kinds of stuff, shooting ourselves in the foot a lot of the time.”

NOTES: S Chris Conte left Thursday’s game with an eye injury, which come on the heels of two concussions and a nagging shoulder injury caused Conte to lose time and rookie fill-in Brock Vereen was a liability in deep coverage. … Also injured in the game were DE Cornelius Washington (chest) and CB Tim Jennings (groin). G Brian de la Puente (ankle) went on injured reserve Thursday, the second left guard lost to injury (Matt Slauson) on a line that has been reshuffled more than a deck of cards in Las Vegas.

REPORT CARD VS. LIONS

–PASSING OFFENSE: C-plus — Jay Cutler managed to avoid interception until the score was 31-17 and the outlook bleak in the second half. His second INT came in the closing moments on a desperation throw. Cutler was asked to execute a horizontal passing game throughout the early part of the game and he did a decent job of this, but when the Bears fell behind he held the ball too long at times on passes that he needed to throw quicker in order to beat cover-2 zone. Tight end Martellus Bennett had a dropped pass but did have 109 yards on eight catches, and Alshon Jeffery was fine catching bubble screens but rarely got open downfield. Considering how ugly this game could have gotten, the offensive line did a respectable job allowing just three sacks.

–RUSHING OFFENSE: F — Five carries by Matt Forte hardly constitutes a rushing attack. The idea was to use the bubble screens and swing passes as a version of the running attack in order to beat Detroit’s defensive line quickness, but it’s still not the same thing as a running back running through tackles and pounding on would-be tacklers.

–PASS DEFENSE: F — By allowing Matt Stafford to throw for 276 first-half yards, the Bears’ defense let the Lions turn the game back in their favor. Kyle Fuller failed in an attempt to cover Calvin Johnson one on one all over the field. It was something the Bears had frequently thought they could do with Charles Tillman, and he usually achieved it. But Fuller did it because the coaching staff feared the mismatch of 5-foot-8 Tim Jennings trying to cover Megatron. The pass rush, with Jared Allen getting a couple sacks and a fumble forced and fumble recovery early, started strong before vanishing.

–RUSH DEFENSE: A — Detroit tried to run early, and went nowhere with Stephen Paea, Ego Ferguson and Will Sutton shutting it down. The Lions just went to a short passing game and timing attack to make up for this and did it effectively.

–SPECIAL TEAMS: B — The Bears won the field position war, forcing Detroit to start inside its 20 five times — three times on kicks and twice on punts. Robbie Gould finally got a chance at a field goal to break his streak of games without three-pointers, and the return teams played without penalty.

–COACHING: D-plus — Marc Trestman’s game plan had the right approach early with short passes and getting the ball to the outside to keep the Lions pass rush off balance. However, he needed to mix in more runs later in the first half and more longer passes at times as an adjustment needed to be made once they fell behind. Mel Tucker came with an occasional blitz early, but the idea to keep Kyle Fuller one on one with Megatron was ill-advised. While the Bears have plenty of confidence in their rookie, he had never faced Johnson before, was nursing knee and hand injuries and simply isn’t the taller cover corner that Charles Tillman was. They needed more safety help for Fuller. Whether on offense or defense, this team seems to have a real confidence problem when momentum changes in an opponent’s favor. Instead of making a stand and regaining it, the Bears tend to just fade away. Coaching can do a lot for confidence.