It's been nearly three months since the Vikings and Bears last met.

Bears Head Coach John Fox said Minnesota has changed some from the 2-2 squad he last prepared for, stating that the biggest difference is that the Vikings are now "settled in at quarterback."

Case Keenum had started Weeks 2 through 4 prior to the Vikings traveling to Chicago in Week 5. Sam Bradford returned to start that game, however, before re-aggravating his knee injury and leaving the game for Keenum to play the second half.

"I think they're moving the pocket more with Case on a consistent basis than on the prep film we saw getting ready for the game here at Soldier Field," Fox said earlier this week.

Fox believes that Keenum has succeeded in Minnesota for a couple of reasons, one of them being the offensive pieces he's able to work with.

"He has a supporting cast. He has a pretty good trio of receivers [and] tight end," Fox said. "He's got mobility – they've utilized that a lot, moving him outside the pocket."  

When asked specifically about Adam Thielen and his performance this year, Fox called the receiver's season "pretty impressive."

"He's been a guy, he was a college free agent, I can remember getting glimpses of him [my first year with the Bears] in '15, either in special teams or [through] some experiences or reps as a wideout," Fox said. "But he's definitely grown, and he's done a lot. They've done a good job developing him."

And as much as Keenum and the skill players have contributed to Minnesota's success thus far, the offensive line has also been credited for its performance.

In comparing the 2017 Vikings offensive line to that of last season or even years prior, Fox said he notices a different "effectiveness" with the current unit. He pointed out that the Vikings linemen this year fit well into the system run by Vikings Offensive Coordinator Pat Shurmur.

"In the West Coast offense you get the ball out a little bit quicker – when you do increase the depth of the drops, you have more people involved in protection," Fox said.

He added that the line has experienced a handful of injuries throughout the year, including a season-ending ankle injury sustained by left guard Nick Easton at Green Bay.

"But they've done a good job of weathering some of those things," Fox added. "There's been a couple changes along the way in the film breakdown I've done, so I think that's a tribute to their coaching staff and the guys that have been called upon to step in."

Don't forget about the dynamic defense

Fox spoke largely of Minnesota's offense, but he and quarterback Mitchell Trubisky also were asked about the defensive unit that ranks No. 1 both in total defense and scoring defense.

Fox credited Vikings Head Coach Mike Zimmer for the work he's done since taking the reins in Minnesota in 2014.

"Mike's done a great job there," Fox said. "Being in that system as long as they have, they're a well-coached and well-talented defensive football team – from a scheming standpoint and a talent standpoint."

Fox highlighted the Vikings defense on all three levels, starting with the defensive line.

"They present some problems up front, they've got some good-sized guys inside playing at nose and 3-technique," Fox said. "Both ends, you know, they've got a pretty good corps of guys that they wave through there, but their starters are pretty good. I think 97 (Everson Griffen) got us once last game. I think their second-level linebackers are good, athletic, they've been together for a minute, so they're pretty sound. They're not real exotic, but they're pretty sound in what they do."

Added Fox: "They've got a guy who probably should have been in the Pro Bowl, their free safety (Harrison Smith), and then they've got a good corner crew that they've invested a lot of high picks in."

Trubisky is approaching the final game of his rookie season and his second time preparing for Minnesota's defense.

The quarterback made his first start in Week 5 against Minnesota. Also asked about Smith, Trubisky called him the "quarterback of their defense."

"He's getting them lined up, he's a really smart, instinctual player and he's a playmaker," Trubisky said. "He's a ball hawk. He's going to be everywhere – down in the box and making plays in the back end. So you have to account for where he's at, and everyone else.

"They're just a solid defense," Trubisky continued. "They play really well together. We're just going to have to account for those guys, go in with a really good game plan, which we've got this week, practice hard, finish out strong and execute the plays on Sunday."