According to ESPN's Field Yates, the Bears are converting $13 million of Mack's salary and roster bonus into a signing bonus, which will create $11 million in salary-cap space.
After acquiring Mack in a trade with the Oakland Raiders last offseason, the Bears signed him to a six-year, $141 million contract extension.
In his first season with the Bears, Mack registered 47 tackles, 12.5 sacks and a career-high six forced fumbles. He also returned an interception for a touchdown for the second time in his five-year career.
Mack was named a Pro Bowler for the fourth time and received his third All-Pro first-team nod as well.
The 28-year-old provided an instant boost to a Bears team that had struggled mightily in recent years. Mack helped lead Chicago to a 12-4 record and an NFC North title, marking the first time the Bears made the playoffs since 2010.
Chicago fell to the Philadelphia Eagles in the NFC Wild Card Round when kicker Cody Parkey missed a game-winning field goal, but the Bears are positioning themselves to take another step forward in 2019.
As Adam Jahns of the Chicago Sun-Times pointed out, restructuring Mack's deal gives the Bears flexibility:
With no first- or second-round pick in this year's draft, the Bears likely need to make a move in free agency or via trade to improve.
They could use another outside threat to complement Allen Robinson, Taylor Gabriel and Anthony Miller. They would also benefit from a safety to replace Adrian Amos, who will reportedly sign with the rival Green Bay Packers in free agency.
The gap between Chicago and the rest of the NFC North may be closing, with the Packers and Detroit Lions—who are reportedly signing defensive end Trey Flowers, cornerback Justin Coleman, tight end Jesse James and wide receiver Danny Amendola—making splashy moves in free agency.
With Mack's restructuring creating much-needed cap space, the Bears now have a chance to keep up in the arms race and strengthen a team that was among the best in football last season.