By Dan Durkin–

(CBS) The Bears (5-6) host the 49ers (3-8) at Soldier Field for the first time since 2006. Sunday’s matchup presents a prime opportunity for the Bears to get back to .500 against an inferior 49ers outfit.

While the 49ers defense has played better over the past few games, they’ve struggled on the road all season.

Here are a few aspects to focus on during Sunday’s action.

What to watch for when the Bears have the ball

Aggressive through the hole

The 49ers rank 29th in total defense this year, and they’ve been deficient both against the run (121 yards per game, 25th in the league) and the pass (276.8 yards per game, 29th in the league). However, one common thread in their three wins has been their run defense. They’re 3-1 in games in which they’ve held opponents to 77 yards or fewer.

The Bears should attempt to make this game ugly and establish the run. The 49ers are 0-7 in games in which opponents have rushed for 84 or more yards. They’ve given up 139 or more in five of those games, including a 255-yard outburst two weeks ago to Seahawks rookie running back Thomas Rawls.

The 49ers lost one of their best run defenders, defensive lineman Glenn Dorsey, on the first play of the Seattle game to an ACL injury, but as a whole, they’re inconsistent with their gap fits and are sloppy with their tackling at the point of attack. Seattle relentlessly delivered body blows on a mixture of zone, counters and one-back power runs, all of which Chicago uses effectively in its offensive scheme.

With Ka’Deem Carey cleared from the NFL’s concussion protocol, Bears offensive coordinator Adam Gase has three running backs to work with, all with unique skill sets. Look for Matt Forte to be used on zone runs, Jeremy Langford on the perimeter and Carey in between the tackles.

Work Jeffery vertically

Bears defensive coordinator Vic Fangio has been replaced by Eric Mangini in San Francisco, but using safeties interchangeably remains a staple of the 49ers’ defensive scheme. Mangini uses pre- and post-snap rotations to try and disguise his coverages, but it has left the 49ers vulnerable to the deep ball when they’re late getting to their landmark or influenced by routes up the seam.

Opposing No. 1 receivers have had highly productive games against the 49ers, generating several explosive plays. Antonio Brown, Larry Fitzgerald and Odell Beckham Jr. all got vertical against the 49ers in single-coverage situations running straight go routes on the back side of formations.

The 49ers lost Pro Bowl safety Antoine Bethea to a season-ending knee injury in Week 8. He was replaced by rookie Jaquiski Tartt. Both Tartt and his counterpart, former first-round selection Eric Reid, are long, rangy athletes who are big hitters over the middle. However, both have been victimized by quarterbacks looking them off to get them to open their hips in single-high coverage to the opposite side of the vertical route, leaving the deep-third on the backside open.

Bears receiver Alshon Jeffery is averaging 100 yards per game when he suits up. Look for the Bears to influence the 49ers to drop their strong safeties down both with formations and run action to create deep opportunities for Jeffery down the field.

What to watch for when the 49ers have the ball

Stopping the run

Nothing has gone right for the 49ers offense this season, and the statistics bear that out. They rank dead last in points per game (13.8) and yards per game (295.5), are 31st in time of possession (26:47) and offensive points per drive (1.32) and are 30th in passing offense (198.4) and offensive yards per drive (27.7). Numbers that bad embody the overall lack of talent, poor quarterback play and the unimaginative offensive scheme coordinated by Geep Chryst that’s plagued the 49ers this season.

The formula for beating the 49ers is a simple and a tried-and-true plan: stop the run and force their quarterback to beat you, be it Colin Kaepernick or now Blaine Gabbert. The 49ers are 1-8 in games in which they’ve been held to 124 rushing yards or fewer. In their three wins, they’ve rushed for 230, 65 and 133 yards, respectively.

Injuries to running backs Carlos Hyde (foot) and Reggie Bush (MCL) forced the 49ers to bring in street free agent Shaun Draughn to carry the load, which has been heavy. Since joining the 49ers in Week 9, Draughn is averaging 20 touches per game, leads the team in targets (21) and was on the field for each of the offense’s 56 plays last week against Arizona.

Outside of two carries, Draughn’s averaging a mere 2.5 yards per attempt. His lack of burst is a factor, but so is the 49ers’ offensive line, which doesn’t get much movement at the point of attack.

It’s imperative that the Bears’ run defense is stout on early downs to put the 49ers in third-and-long situations, forcing Gabbert to beat them.

Tight third-down coverage

Somehow, Gabbert’s performances over the past three games are being perceived as progress. Part of this is due to just how bad Kaepernick was over the first eight games of the season. But when you watch the tape, Gabbert remains the risk-averse, low-ceiling quarterback that forced the Jaguars to turn the page.

In 31 offensive drives, Gabbert’s led just four touchdown drives, and his careful nature on third down has led to several stalled drives for the 49ers. On third down, Gabbert has gone 17-for-31 for 199 yards with two touchdowns and one interception while taking three sacks. Of those 17 completions, 11 were thrown short of the sticks.

The 49ers’ offensive line woes aren’t limited to the run game. They’ve given up 35 sacks, which ranks 31st in the league. Their weak link has been right tackle Erik Pears, who has given up eight sacks.

Look for the Bears to tighten up with press-man coverage on third down to challenge the releases of outside receivers. Gabbert has a tendency to read the field low to high, even on third down. This could lead him to taking short throws — tight end Vance McDonald has become one of his favorites — and relying on receivers to make yards after the catch to convert.

Over the course of a game, that approach is typically a losing formula, particularly with the limited targets Gabbert has to throw to.

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