The Bears' 41-15 preseason loss to the Bills Saturday at Soldier Field left plenty of room for improvement.

The Bears struggled on both sides of the ball. They failed to convert all 11 of their third-down plays, allowed touchdowns on Buffalo's first four possessions and committed 10 penalties for 73 yards.

The Bears played without several key starters, resting receivers Allen Robinson II and Darnell Mooney, running back David Montgomery, tight end Cole Kmet, nose tackle Eddie Goldman and inside linebackers Roquan Smith and Danny Trevathan.

The Bills dominated the first half, taking a 34-6 halftime lead. Buffalo scored touchdowns on its first four possessions, produced points on six of seven drives and held decisive advantages in first downs (19-4) and total yards (279-145).

Coach Matt Nagy wasn't overly exuberant after last weekend's win over the Dolphins and won't be too downtrodden following Saturday's loss. But he knows that the Bears must play better than they did versus the Bills.

"I am happy that it's preseason so that we can evaluate," Nagy said. "I know we all want to win. But it's like last week: we felt good and there's a high, but you gotta be careful with that. We want to make sure that we stay right in the middle ground and understand that today wasn't good enough. That's my job to make sure that we're better. We have to practice better. We have to play in the game better, and in the end, the evaluation process for us is to see where these guys are, and now we're a week away from making more [roster] decisions."

With the Bills resting starter Josh Allen, former Bears quarterback Mitchell Trubisky played the entire first half, completing 20 of 28 passes for 221 yards with one touchdown and a 106.4 passer rating. The Bears defense repeatedly allowed Trubisky to complete short, quick passes over the middle and missed several tackles.

The Bills raced to a 28-0 lead with TDs on Devin Singletary's 14-yard run, Trubisky's 4-yard pass to Jake Kumerow and a pair of Reggie Gilliam 1-yard runs. After the Bears defense finally stopped Buffalo with a three-and-out, Bills kicker Tyler Bass added field goals of 33 and 41 yards in the final :74 of the half.

The Bears, meanwhile, failed to score on six of seven first-half possessions. They had three three-and-punts, committed two turnovers on an Andy Dalton interception and a Damien Williams lost fumble, and turned the ball over on downs.

The offense's lone first-half score came on Dalton's 73-yard touchdown pass to receiver Rodney Adams, who snatched the well-thrown ball off the helmet of safety Siran Neal and raced to the end zone. The TD accounted for more than half of the Bears' yardage in the first half; they mustered just 72 yards on their other 22 plays.

"We didn't get in too much of a rhythm early," Dalton said. "We'd like to be a little more efficient and more consistent with our performance. It was nice to get the deep ball to Rodney. He made an unbelievable play."

Dalton completed 11 of 17 passes for 146 yards with one TD, one interception and an 86.9 passer rating in the first half.

The Bears didn't allow the Buffalo offense to score a touchdown in the second half. But the Bills increased their lead to 41-6 nonetheless as Marquez Stevenson returned a punt 79 yards for a touchdown midway through the third quarter.

The Bears responded by marching to the Buffalo 7, as Justin Fields scrambled for 16 yards on fourth-and-3 and 11 yards to the 7. But the rookie quarterback threw back-to-back incompletions intended for Jesse James and Adams on third- and fourth-and-goal from the 9.

The Bears scored their second touchdown of the game early in the fourth quarter on rookie Khalil Herbert's 13-yard run, cutting the deficit to 41-12. The score came one play after blitzing linebacker Andre Smith drew a 15-yard penalty for a vicious helmet-to-helmet hit on Fields that knocked the quarterback's helmet off and elicited boos from the crowd.

Bears backup kicker Brian Johnson drilled a 54-yard field goal with 5:29 remaining in the contest, closing the gap to 41-15.

The Bears generated two takeaways in the fourth quarter, both on fumble recoveries by rookie inside linebacker Caleb Johnson. The second came on a strip/sack by second-year outside linebacker Trevis Gipson against Bills third-string quarterback Davis Webb.

Playing the entire second half, Fields completed 9 of 19 passes for 80 yards and a 59.1 passer rating. He also led the Bears in rushing with 46 yards on four carries.