The heart and soul of the Kansas City Chiefs defense, Tyrann Mathieu, has one year left on the three-year, $42 million contract he signed in 2019.

Most figured the 2020 Pro Bowler and first-team All-Pro, who intercepted six passes and recorded 62 tackles last season, was due for an extension.

But then the 29-year-old Mathieu posted an ominous tweet, indicating he might not remain with the Chiefs beyond 2021, which he then deleted.

“The negotiation process is — it’s tough on anybody,” Mathieu said. “This is my third franchise. So I understand the business.”

His friend and defensive back mate the last two years, Bashaud Breeland, can relate.

Breeland, who is also 29, remains a free agent after signing three consecutive one-year deals the last three seasons.

He signed a one-year, $880,000 contract with the Green Bay Packers for the 2018 season, a one-year, $2 million contract with the Chiefs for the 2019 season and a one-year, $3 million contract with the Chiefs for the 2020 season.

Because teams knew he would miss four games in 2020 after violating the league’s substance abuse policy, Breeland had to know his value would be diminished last year. And then his prospective finances took another hit this season when the 2021 salary cap was set at 182.5 million. That 8% decrease from the previous year will further squeeze teams’ resources.

Still Breeland, a physical 5-11, 195-pounder who can play both nickel and outside cornerback, should serve as an enticing addition for some NFL team. 

“He’s one of the more underrated cornerbacks in this league,” Mathieu said, “being able to play press-man, bump and run with elite receivers.”

Breeland has been a bit of boom or bust player with the Chiefs the last couple of seasons.

He mixes key interceptions with untimely penalties. Of note is that he’s played well against Tom Brady, intercepting the legendary quarterback in two of the last three games he’s played against him.

In the locker room, Breeland and Mathieu served as divergent personalities. The former’s more laid-back, fun-loving demeanor often bore witness to Mathieu’s wired up, pregame intensity.

“Breeland sits there,” Chiefs defensive backs/cornerbacks coach Sam Madison said. “He laughs at him.”

Mathieu was the leader in the secondary last year, often welcoming the defensive backs over to his home to help mentor them, but he was particularly friendly with Breeland.

“I try to keep a close relationship with all my guys,” Mathieu said. “Me and Breezy is probably a little different. We talk more than others.”

Mathieu made it sound like the door is not shut on his friend’s return to Kansas City.

“I hope we can get him back here,” Mathieu said. “A lot of things aren’t in our control. I just try to continue to be a positive influence in his life and just continue to encourage him no matter what.”

Similarly, Mathieu’s deleted tweet doesn’t mean he’s destined to end his NFL career elsewhere.

Chris Jones had a similarly negative tweet last year, in which he implied he would hold out, but ended up signing a four-year, $80 million deal with the Chiefs before training camp began.

Jones may be the defense’s best player, but Mathieu is the most versatile. He plays safety, cornerback, blitzer and even linebacker. He’s also the vocal leader.

And he won’t let any future uncertainty get in the way of his preparation for the 2021 season.

“I try not to focus on it too much,” Mathieu said. “I understand the business. I’m grown enough to understand it. I think I’m mature enough to understand it. But I’m also mature enough to understand that there’s still a lot of work that I’ve got to put in.”