By Dan Durkin-

(CBS) Heading into the 2014 season, one of the biggest concerns for the Bears was their run defense. Last season, they gave up 2,583 rushing yards and 22 touchdowns, allowed 11 running backs to rush for 100 or more yards and finished as the only team in the league to allow more than five yards per carry.

Through six games, the Bears rank 10th in the NFL (fifth in the NFC) against the run, giving up 103 yards per game, and have yet to allow a 100-yard rusher. In fact, the highest individual rushing total so far this season against the Bears hasn’t even come from a running back; it was 49ers quarterback Colin Kaepernick’s 64 yards in Week 2.

Against Atlanta, Chicago gave up 14 yards on the Falcons’ first play from scrimmage, then proceeded to limit it to 28 yards on its next 12 carries. The 42 total rushing yards allowed was the lowest total of the season for the Bears, and it coincided with the return of defensive tackle Jeremiah Ratliff from injury. The Falcons had nine carries in between the tackles — the area in which Ratliff operates — for a mere 16 yards, per ProFootballFocus.

“He’s an outstanding player for us — he’s one of our leaders,” defensive coordinator Mel Tucker said. “He’s very stout in the run game and gives you excellent push in the passing game in terms of the pass rush. He’s a bell cow type of guy — a guy that you can rally around. You know exactly what you’re getting from him day in and day out. He brings the productivity, the mental and physical toughness and attitude that we like to see in the middle of our defense. He’s an excellent player.”

Defensive end Jared Allen said that the opportunity to play next to Ratliff weighed into his decision to sign with the Bears.

“Jay makes all the difference in the world,” Allen said. “Having him and (Stephen) Paea in there at the same time — and not taking anything from Ego (Ferguson) and Will (Sutton), they’ve been playing great in his absence — but Jay, I was excited to come play with Jay because I’ve been watching him play for years, and when he’s healthy, that dude is strong. He’s technical, he’s capable. There’s not a whole lot of guys who are capable of changing game from a DT position, but he’s one of them.”

The Dolphins — who the Bears host Sunday afternoon — rank sixth in the league in rushing but have lost Knowshon Moreno for the season. With Miami’s zone-read attack, Allen will have to be on his game. Allen’s made his name as a pass rusher, but in his mind he’s always been stout against the run.

“I don’t know where this whole theory started,” Allen said. “I think it was Gunther (Cunningham) — I love Gunth to death — but he started this nasty rumor that I couldn’t play the run. Go back and watch the film I’ve been smashing the run for a long time.”

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