The Kansas City Chiefs may have won 12 games and advanced all the way to the AFC Championship Game this past season, but it certainly was not because of their defense.

The Chiefs ranked second-to-last in the NFL in total defense and 24th in scoring defense in 2018, compensating for their obvious defensive shortcomings with a high-powered offense led by Patrick Mahomes.

This offseason, Kansas City did not really get any better on the defensive side of the ball, as while the Chiefs did add Frank Clark and Tyrann Mathieu, they lost Dee Ford and Justin Houston, so it was more like they were just trading talent for talent.

But with Kareem Hunt gone and Tyreek Hill seeming likely to miss the entire 2019 campaign, more pressure will fall on the shoulders of Kansas City's defense to produce, as the offense probably won't be as explosive as it was a year ago.

Enter Mathieu, a rather tragic player who was once one of the most dominant defensive players in the league but quickly saw injuries take their best shot at derailing him.

It's not that Mathieu is a bum at this point; he is still a solid safety and is coming off a 2018 campaign with the Houston Texans in which he recorded 89 tackles, three sacks, a couple of interceptions, a fumble recovery and eight passes defended, but the days of Mathieu being a constant ballhawk in the secondary seem to be over.

The 27-year-old suffered multiple knee injuries over the first three seasons of his NFL career with the Arizona Cardinals, first tearing his ACL and his LCL in 2013 and then tearing his ACL again in 2015, the year he made the Pro Bowl and earned a First-Team All-Pro selection.

Since then, it has been a struggle for Mathieu. He can't move like he once did, his explosiveness is not there anymore and his reaction time is significantly slower than it was four or five years ago.

That is to be expected for a guy whose knees have seen enough wear and tear that most people see in a lifetime, but due to his instincts and football IQ, Mathieu has remained a productive safety who can still be a key component of a defense.

But if the Chiefs are expecting him to star for them, they are probably going to be disappointed.

The fact of the matter is that Kansas City is not getting the Tyrann Mathieu we saw in 2015. They are getting an older, more beat-up version of that player. And while Mathieu did have a very solid bounce-back season in 2018, he is no longer a player capable of carrying a defense on his own, especially a defense as troubled as the Chiefs' unit.

Kansas City will once again be relying heavily on its offense going into 2019, which is not much different from this past year. The problem is, the Chiefs may not be able to mitigate their defensive struggles as well as they did in 2018, and it's hard to see Mathieu changing that.

Mathieu is unquestionably smart, dedicated and resilient, but you can't deny the fact that injuries have taken a toll on him that he will never fully recover from.