He sees the weapons they possess, the receivers and strong-armed quarterback they have and the Arizona Cardinals defensive back wonders what everyone else wonders. He's surprised he hasn't seen more explosive plays out of Detroit.
Now, unlike a lot of Lions fans, this is good news for Mathieu, as he is the latest defensive back who is trying to make sure that trend continues.
"I'm very, very, very surprised. When you look at those guys' personnel on offense, Calvin Johnson and Golden Tate, those two guys alone have you raising eyebrows as to wondering why they haven't been putting up a lot of points this season," Mathieu said. "They are one of those teams, man, that they look out of sync right now.
"But they'll find their rhythm at some point during the season."
Facing the Cardinals would not seem like the time that would happen. Arizona has the No. 5 defense in the league and the No. 8 passing offense in the NFL. They have a star cornerback in Patrick Peterson and one of the most versatile defensive backs in the league in Mathieu. The defensive backfield already has six interceptions and the Cardinals have the No. 1 interception percentage in the NFL (5.7 percent).
Taking big, explosive shots comes with an extra level of peril normally when facing Arizona -- the fourth top-10 pass defense the Lions will face in five games. Taking those chances when you're offense is No. 30 in the league in yards per game and has the worst rushing offense in the NFL is even more dangerous.
But when Mathieu sees Detroit's players and says they look out of sync offensively, he means that he feels they should be far more productive.
"You talk about their personnel and it's not like those guys have a bad quarterback," Mathieu said. "They have Matthew Stafford back there. They have some pretty good running backs. They have some pretty good wide receivers.
"For me, they just look like they don't quite understand the system yet, so to say, because you think about it, man, those guys, man, they could easily put up 30 points a game."
The Lions instead have put up a little bit more than half that -- 16.5 points a game -- and are outscoring just Miami, Jacksonville and San Francisco. Meanwhile three teams, including Arizona, are doubling Detroit's average points per game this season.
And Mathieu isn't the only one surprised by Detroit's offensive woes, especially considering the arm strength Stafford typically has.
"That always surprises me. I think he's one of the best in the business," Arizona coach Bruce Arians said. "I love going out and watching him warm up because he can make every throw in the book and he's a great kid. You know in the fourth quarter, that's his time. He loves to play in the fourth quarter.
"I thought they should have won that, that was a great drive the other night. It's a shame they didn't win the game."
The drive Arians is talking about was Detroit's final one against Seattle, where Stafford was perfect, completing all six of his passes and driving the Lions 90 yards before Calvin Johnson fumbled at the 1-yard line, the ball was batted out of bounds intentionally and controversy ensued during the Seahawks' 13-10 win.
The Lions did take more deep chances against Seattle, but none really connected -- including two that appeared to be thrown too far for Johnson and one that was almost intercepted when thrown in double coverage to Tate.
Those have been some of the few deep chances the Lions have taken this season -- and opponents have noticed, especially with Johnson.
"One of the things that jump out early on is they are not taking as many shots downfield with him as they would normally do," Mathieu said. "That's pretty obvious once you turn on the tape."
The chances the Lions took Monday night, though, told Mathieu they are going to potentially start trying to more often.
It showed offensive pass diversification for a team averaging 6.13 air yards per attempt -- second-lowest in the NFL.
But it marked the first game Stafford failed to throw a touchdown since Week 16 of last season against Chicago. It is also the last game the Lions won.
While the Lions didn't score offensively, they appeared to make progress in an attempt to ignite the offense -- something both Stafford and Johnson deemed important Wednesday because they both know hitting on a few of those can open up the rest of the offense.
Stafford and Johnson have seen it happen many times before.
"Yeah, we've just gotta keep on taking them," Johnson said. "Back that defense up so they're not playing or sitting on routes, whatever it may be.
"But yeah, definitely you should take those early and often."