The Bears completed a blockbuster trade with the Oakland Raiders Saturday, bolstering their defense in a monumental way by acquiring star pass rusher Khalil Mack.

The Bears acquired the 2016 NFL defensive player of the year and three-time Pro Bowler along with a 2020 second-round pick and a conditional 2020 fifth-round pick in exchange for their 2019 first-round pick, 2020 first-round pick, 2020 third-round pick and 2019 sixth-round pick.

"We are excited to add a special playmaker like Khalil to our football team," said Bears general manager Ryan Pace. "He brings a ton on the field, but he really fits what we are building in our locker room, too. Elite defensive players in their prime are rare so when we knew we had a legit shot to acquire him, we did everything we thought necessary to get him. I'm confident the compensation to Oakland, including the return draft picks to us, and the contract extension for Khalil are fair to all parties. We are anxious to get Khalil to Chicago with his coaches and teammates."

Mack was selected by the Raiders with the fifth overall pick in the 2014 draft out of Buffalo. Starting all 64 games the past four seasons, the 6-3, 252-pounder has compiled 327 tackles, 40.5 sacks, one interception, 17 pass breakups, nine forced fumbles and four fumble recoveries.

A two-time All-Pro, Mack has been voted to the Pro Bowl each of the past three seasons after recording 15.0 sacks in 2015, 11 in 2016 and 10.5 in 2017. The last Bears player to reach double digits in sacks was Willie Young with 10.0 in 2014.

Mack's 36.5 sacks over the past three seasons rank second in the NFL. Last year he was the only defensive player in the league to tally at least 75 tackles, 10 sacks, five passes defensed, one forced fumble and one fumble recovery.

The only Bears players who have recorded more career sacks than the 40.5 Mack has compiled in his first four NFL seasons are Richard Dent (124.5), Steve McMichael (92.5), Dan Hampton (57), Alex Brown (43.5), Adewale Ogunleye (42.0), Trace Armstrong (42) and Brian Urlacher (41.5).

Mack made NFL history in 2015 by becoming the first player to be named first-team All-Pro at two positions (defensive end and outside linebacker). His 15 sacks that season were the second most in the NFL.

Mack had been holding out with the Raiders; he did not participate in Oakland's offseason program, training camp or preseason games while seeking a new contract. The Bears signed Mack to a lucrative six-year extension through 2024.

The 27-year-old Florida native joins a Bears defense that ranked ninth in the NFL in points allowed and 10th in total yards last season under coordinator Vic Fangio.

The unit also added Georgia inside linebacker Roquan Smith with the eighth pick in this year's draft. Both players have recently won the Butkus Award, Mack as the NFL's best linebacker in 2016 and Smith as college football's top linebacker in 2017.

The Bears now have three players on their defense who were selected with top 10 picks in the draft in Mack, Smith and outside linebacker Leonard Floyd (No. 9 in 2016). Two others were also chosen in the first round, cornerbacks Kyle Fuller (No. 14 in 2014) and Prince Amukamara (No. 19 by the Giants in 2011).