A week after the Buffalo Bills blew them out, the San Francisco 49ers had their own chance to play bully.

Hosting the Chicago Bears in Chicago’s first game since firing head coach Matt Eberflus, the 49ers took advantage of a discombobulated opponent to win 38-13 in a game that quickly became one-sided.

The rebound may not be sufficient to save San Francisco’s slim playoff chances. But the performance should encourage the 49ers as they enter an offseason in which they can negotiate with quarterback Brock Purdy, and it should remind the 49ers that they’re far more capable than their recent skid suggested.

The Bears, meanwhile, fell to 4-8 with their seventh straight loss and first under interim head coach Thomas Brown. The offense regressed from its recent improvement and the defense looked thoroughly lost without its defensive play-caller. Their schedule only gets tougher from here.

The 49ers opened by marching down the field with an explosive attack. Running back Isaac Guerendo took a dump-off 23 yards on one play and Purdy found tight end George Kittle for 33 on the next play. Just five plays into the game, fullback Jauan Jennings cut out to the left to score the game’s first touchdown.

The Bears responded with a three-and-out.

The 49ers’ second touchdown drive proved just as seamless as the first. Guerendo and Kittle again burned Chicago’s defense despite the absence of 49ers playmakers like Christian McCaffrey, Brandon Aiyuk and Jordan Mason.

Were the Bears shaken from their organizational shakeup, or perhaps not receiving defensive instructions as clearly in the wake of their head coach and defensive play-caller departing?

Jennings stutter-stepped his defender out of rhythm to catch and run in a 16-yard touchdown with 12:20 to play in the second quarter.

By halftime, the game was even more lopsided than its 24-0 scoring margin looked.

Chicago’s measly four yards was the Bears’ smallest first-half output since 1991, per the broadcast; the 315-yard differential marked the largest of any NFL game this season at halftime.

The Bears’ 0.2 yards per play were the third-lowest first-half yardage average since 2012, per TruMedia Sports.

Bears’ second-half improvement too little, too late

The Bears shifted to a more balanced attack to open the second half after the pass-heavy product in the first half subjected Williams to four sacks.

Reintegrating the run helped the Bears set up more favorable third-down attempts, with Chicago extending their drive for more than nine minutes of the third quarter.

And when Chicago reached the end zone, Williams dropped back on third-and-goal to hit fellow rookie Rome Odunze on an out route for a four-yard touchdown. Odunze caught an airborne pass in the back right corner of the end zone, careful to get both feet in before he fell out of bounds.

The two-point conversion attempt slipped through tight end Cole Kmet’s arms, but Chicago’s defense forced a punt to maintain momentum … until Williams let a backward pass slip from his hands, 49ers coach Kyle Shanahan challenging the initial incomplete pass ruling that would be overturned. San Francisco defensive tackle Evan Anderson recovered the fumble.

The 49ers converted their turnover-gifted possession into yet another touchdown. And then: Williams found Odunze yet again for a second score. But it was too little, too late.

The 49ers would pull their starters before the clock expired.

Bears safety Jonathan Owens, who is married to Simone Biles, intercepted 49ers backup Brandon Allen with 1:59 to play.

Purdy completed 20-of-25 pass attempts for 325 yards, two touchdowns and no interceptions. Kittle led all weapons with 151 yards on just six targets. He caught all of his targets for more than 10 yards, including three for 30-plus.

Guerendo, in the lead back role after McCaffrey and Mason’s injuries, added 128 yards from scrimmage.

Williams completed 17-of-23 passes for 134 yards and two touchdowns. He took seven sacks, bringing his yearlong total to a league-high 56.