The Chicago Bears brought back the feeling of the 1985 Bears' defense last season. With Khalil Mack leading the way, opposing offenses had a tough time escaping their dominance. One of the crucial pieces of Chicago's defense—playing the same position Mike Singletary did—is Roquan Smith.

Heading into the 2019 season, Smith will be the X-Factor for the Bears on defense. Why Smith, you might ask? Because his role on the defense is vital to the defense performing at its highest potential.

In most defenses, the middle linebacker usually is the quarterback of the defense. Therefore, Smith could be tasked with calling the plays for the defense in 2019. Last season, Danny Trevathan was given the responsibility of calling the plays.

Smith's rookie season last year got off to a shaky start after the linebacker held out for the majority of training camp. In the end, both the Bears and Smith came to an agreement and Smith earned minimal playing time in the preseason. Then, Smith was put into a reserve role to kick off the season.

Vic Fangio—the Bears' defensive coordinator in 2018, now the Denver Broncos' head coach—showed Smith he was going to have to earn his role despite being taken with the eighth overall pick. After just one game, Smith got the opportunity to start in Week 2 against the Seattle Seahawks.

The rookie linebacker finished the game with seven tackles and a pass deflection. It was one of many impressive games for Smith during his rookie campaign. At the end of the season, he may not have won the Defensive Rookie of the Year Award, but his stats spoke for themselves.

Smith racked up 121 total tackles, five sacks, eight tackles for loss, and an interception in 2018. Therefore, expectations are understandably high for the former first-round selection out of Georgia.

In 2019, the Bears decided to replace Fangio with Chuck Pagano. Pagano comes from a background of being a successful defensive coordinator. Most notably, Pagano helped lead the Baltimore Ravens to the top tier of the NFL, guiding the Ravens to the ranking of the NFL's third-best defense in 2011.

On that Ravens defense, Pagano had an all-time great in Ray Lewis to man his defense. With both Trevathan and Smith learning a new defense, Smith could end up being relied upon as the captain of the defense.

Again, the Bears were stifling on defense in 2018. Last season, Chicago was ranked third in total defense (seventh against the pass, first against the run).

The Bears pride themselves on stuffing the opposing team's rushing attack. Smith plays a key role in doing just that in the middle of the defense. If the defense hopes to repeat its success from 2018, Smith will need to step up even more in 2019.

Of course, Mack, Akiem Hicks, Leonard Floyd, Kyle Fuller, and Eddie Jackson will be important as well. Nonetheless, Smith will need to rally the defense to perform at a high level once again for the Bears in the upcoming season.

With the Bears setting their sights on a Super Bowl run, Smith will need to be one of the team's best players. After all, that is why Smith will be the X-Factor for the Bears in 2019.