Ian Rapoport of the NFL Network reported the new pact is expected to "eclipse the deal" given to Los Angeles Rams lineman Aaron Donald on Friday (six years, $135 million). ESPN's Adam Schefter first reported there was an agreement in place between the Raiders and Bears for Mack.
Mack, who missed the entirety of training camp and the preseason while seeking a new deal, could be available for Week 1. The Bears open the campaign with a clash against the rival Green Bay Packers in a nationally broadcast game next Sunday night.
"I miss it," Mack wrote Thursday on Twitter as he remained sidelined while trade rumors swirled.
The 27-year-old University at Buffalo product's track record includes three Pro Bowl selections and two First Team All-Pro nods in addition to a Defensive Player of the Year honor since the Raiders chose him with the fifth overall pick in the 2014 draft.
Mack, who's appeared in all 64 regular-season games over the past four years, racked up 78 tackles and 10.5 sacks in 2017. Pro Football Focus graded him as the league's sixth-best edge defender.
He'll join an already solid Bears defense that ranked 10th in yards allowed and seventh in sacks last season. He should slide back to outside linebacker in his new team's 3-4 defensive scheme, which is a better fit for his all-around skill set than being used as a pure pass-rushing asset at defensive end.
After facing Green Bay in the opener, Chicago moves on to face the Seattle Seahawks on Monday Night Football in Week 2, putting Mack in the national spotlight two straight weeks after the blockbuster trade.