The Bears stumbled out of the gate and were plagued by costly penalties in a disappointing 20-10 loss to the Lions Saturday in Detroit. Here are three things that stood out in the Week 15 defeat:

(1) After the Bears offense took a huge leap forward a week earlier in a 33-7 drubbing of the Bengals, the unit took just as big of a step backward against the Lions.

It was unrealistic to expect the Bears to repeat their performance from a week earlier in Cincinnati when they recorded season highs with 33 points, 482 yards and 29 first downs. But the regression by the offense in Detroit was significant and troubling. The unit did not cross the 50-yard line until 2:00 remained in the first half, didn't reach the red zone until the fourth quarter and didn't score a touchdown until there was 2:32 left in the game.

Mitchell Trubisky entered the game with four interceptions in nine starts and nearly matched that total with three picks against the Lions—all in the second half. "[In Cincinnati] we had a little juice, executed, had things rolling," Trubisky said. "[Saturday] it seemed like the opposite. We've just got to go back, be critical on film to see what I can get better at and continue to push my teammates to get better."

Trubisky didn't receive much help from a running game that was held to 43 yards on 15 carries after producing 222 yards on 30 attempts in the first meeting of the season with the Lions Nov. 19 at Soldier Field. Jordan Howard rushed for 37 yards on 10 carries, while Tarik Cohen had one yard on two attempts. "They have two of the really better backs in combination in terms of running the ball as they have in the league," said Lions coach Jim Caldwell. "They ran for 222 yards on us last time, so that was extremely important and I thought our guys did a good job filling the lanes and gaps, running through, making tackles. The defense did a nice job there."

(2) The Bears repeatedly shot themselves in the foot in all three phases, committing season highs with 13 penalties for 97 yards.

Trailing only 13-0 late in the first half, Cohen returned a kickoff 90 yards to the Detroit 14. But the play was nullified by a holding penalty on DeAndre Houston-Carson and the Bears started at their own 10, a difference of 76 yards.

"The guys upstairs felt it was a good block; it was behind," said coach John Fox. "It was a stretch in the jersey; that's the way it was described to me."

In the first half, penalties on cornerbacks Kyle Fuller and Prince Amukamara on third-down incompletions resulted in automatic first downs, sustaining Lions drives that resulted in a field goal and a touchdown, respectively.

Backed up at their own 8 early in the fourth quarter, the Bears drew three straight flags—two for holding on center Hroniss Grasu and receiver Joshua Bellamy followed by a delay of game that pushed the ball back to the 1.

"Everyone's just got to make a conscious effort to say we're not going to make penalties anymore, we're going to play clean football," Trubisky said.

"You can't have those penalties," added receiver Kendall Wright. "We're putting our offense in bad situations and coming at situations like first-and-15 at the 2. We just can't do that. It's hard to win like that and it's hard when your offense has to start back there. What play can you really call back there? We've just got to stop the penalties and mental mistakes and just play how we played [against the Bengals] and just have fun."

(3) Trubisky made some impressive throws, but also committed some costly rookie mistakes that the Bears hope he will learn from as his development continues.

The rookie quarterback recorded his first 300-yard game, completing 31 of 46 passes for 314 yards. Trubisky flashed the arm talent on some throws that helped convince the Bears to move up to select him with the second pick in the draft. A couple of those laser beams resulted in a 22-yard completion to Markus Wheaton on third-and-18 and a 19-yard strike to Bellamy.

But Trubisky also committed some miscues that seemingly provided evidence of his inexperience. The costliest one occurred early in the fourth quarter with the Bears trailing 20-3. On third-and-goal from the Detroit 5, Trubisky's ill-advised pass intended for receiver Dontrelle Inman was intercepted in the back of the end zone by safety Quandre Diggs. It appeared that Trubisky never saw Diggs sinking back in zone coverage on the play.

"I just lost him in my vision and I thought I had [Inman] in the back of the end zone, so I kind of just forced one there," Trubisky said. "Good coverage and call by them. I've just got to throw the ball away so we can get a field goal and not force it."