During his weekly media session Thursday, Vic Fangio discussed facing the NFL's No. 1 offense, what he's enjoyed most about coaching Khalil Mack and Eddie Jackson's growth.

Here are five things we learned from the Bears defensive coordinator:

(1) The Bears will be challenged by a Buccaneers offense that ranks first in the league in total yards and passing yards, but Fangio's defense faces a big test every week.

"You get 16 final exams in this league," Fangio said. "Yeah, it's a test, but the first three games were a test and the next 12 after this will be a test."

The Buccaneers are averaging 473.3 total yards and 400.7 passing yards through the first three weeks of the season. Ryan Fitzpatrick has fueled the prolific start, becoming the first quarterback in NFL history to pass for at least 400 yards in three straight games.

"These guys are really good," Fangio said. "They've put up the numbers and I think what gets lost in it a little bit is who they've put it up against. They've put it up against three teams (the Saints, Eagles and Steelers) that most people had in their bucket as Super Bowl contenders, and they've gone out there and played really, really well, set some records, some personal records. They're throwing it around and moving the ball on offense really, really good."

(2) Mack is off to an incredible start, but Fangio has been just as impressed with how the All-Pro carries himself off the field as how he's performed on the field.

Asked what he has enjoyed most about working with Mack, Fangio said: "Well, his play No. 1. But I think what I've enjoyed most about him is the guy does not have an ounce of prima donna in his body. He's a joy to be around. The other players like being around him. The coaches like being around him. Besides his talent and production, which everybody sees, he's really a breath of fresh air to be around, too, on a daily basis."

Mack has dominated since being acquired by the Bears in a blockbuster trade with the Oakland Raiders. He's tied for the NFL lead with four sacks, tops the league with three forced fumbles and returned an interception for a touchdown in the season opener in Green Bay. His presence has elevated the performance of the entire defense, which leads the NFL with 14 sacks and is tied for tops in the league with seven forced fumbles.

Fangio feels that Mack's teammates gravitate to him because of his talent, love of the game and attitude. "He's for the team," said the Bears defensive coordinator. "That stuff's contagious."

(3) After a solid rookie season, Jackson's experience and increased comfort in the defense have enabled the second-year pro from Alabama to take his game to the next level.

Jackson has shown the speed and instincts to excel at safety since he joined the Bears last year as a fourth-round draft pick from Alabama. But if he seems a little faster and a little smarter in his second season, it's only because he has gained more familiarity with the defense.

"He's made that jump from rookie season to second year, and he's a little bit better at everything," Fangio said. "He feels a little more comfortable in the system, what we're asking him to do. Anytime a player does that, they can uplift their game to another level because mentally they know more, their recognition time has quickened, and that's what he is doing."

In last Sunday's win over the Cardinals, Jackson recorded his first interception of the season and third of his career. Later in the game, he picked off a second pass and returned it for a touchdown, but the play was nullified by an offside penalty against Mack.

(4) Fangio lauded veteran defensive back Sherrick McManis for the contributions the special-teams standout made on defense in last Sunday's win over the Cardinals.

The longest tenured player on the Bears roster, McManis delivered when called upon on defense in Arizona. He played only five snaps, but produced two huge plays.

First, McManis dove to intercept a Sam Bradford pass at the Cardinals' 44, a turnover the Bears converted into a field goal that cut Arizona's lead to 14-13 late in the third quarter. McManis later clinched the victory by recording his first career sack on the game's final play, dropping rookie quarterback Josh Rosen on a blitz as time expired.

"Well, he's a team guy, first and foremost," Fangio said. "He's tough. He's fast. He's athletic. I'm just happy for his success. He's a guy that based on the way he plays special teams, he should be able to have a role on defense. [Since] the end of last year, we've been carving out a role for him, and I'm not afraid to use him."

(5) Undrafted rookie cornerback Kevin Toliver II*, who could see expanded playing time Sunday due to* Prince Amukamara*'s injury, looked like he belonged against the Cardinals.*

"He had 20-some [snaps], I think," Fangio said. "I thought he did fine. They went after him a little bit there towards the end. We helped him some. Sometimes we didn't. I thought he responded well. They got some balls in front of him, and he got double-moved. So it was a baptism under fire. But I didn't see a guy who looked out of place. And I'm glad he got those 20-something reps because I think it helps him for this week."

Toliver arrived at LSU as a five-star recruit. He played in 31 games with 18 starts over three seasons, compiling 84 tackles and two interceptions. Last season as a junior he appeared in 12 games with five starts, collecting 28 tackles, one interception and one sack.