Bears outside linebacker Khalil Mack has been named the NFC defensive player of the month for September for his performance in the first four games of the season.

Mack ranks second in the NFL with five sacks and tops the league with four forced fumbles. He has recorded a strip/sack in each of the first four games and returned an interception for a touchdown in the season opener in Green Bay.

The fifth-year pro is the first NFL player with a sack and a forced fumble in four straight games since the Colts' Robert Mathis in 2005. Mack is also the first player to record four forced fumbles in the first four weeks of the season since the Jaguars' Tony Brackens in 1999.

The Bears acquired Mack Sept. 1 in a blockbuster trade with the Raiders. He did not participate in Oakland's offseason program, training camp or preseason games. But Mack starred in the Sept. 9 opener against the Packers, registering takeaways on back-to-back possessions.

First, he wrestled the ball away from backup quarterback DeShone Kizer while sacking him. The new Bears star followed by intercepting a pass that Kizer dumped over the middle. Mack then showed the elusiveness of a running back while returning the pick 27 yards for a touchdown.

In the process, he became the first player in NFL history to record a sack, forced fumble, fumble recovery, interception and touchdown in one half.

In a Week 2 win over the Seahawks, Mack produced an impressive strip/sack of quarterback Russell Wilson. Engaged with a blocker, the outside linebacker reached out with one arm and swatted the ball out of Russell's hand.

Mack had another outstanding game in a Week 3 victory in Arizona, recording a team-leading five tackles and two sacks while also compiling one forced fumble, three quarterback hits and one tackle-for-loss. It was the 10th multi-sack outing of Mack's five-year NFL career and his first with the Bears.

Mack produced his fourth strip/sack of the season in last Sunday's win over the Buccaneers when he swatted the ball away from Ryan Fitzpatrick. The Bears star later deflected a Jameis Winston pass that was intercepted by outside linebacker Aaron Lynch.

"Oh my goodness, the Mack attack," said cornerback Prince Amukamara. "Usually the quarterback has about three seconds to throw the ball. [With Mack] it feels like it's about two. He helps us on the back end. We're trying to help him by covering guys. It's no surprise that he really improves our defense."

Mack has helped the Bears win three straight games for the first time since they opened 3-0 in 2013. They are currently in first place in the NFC North with a 3-1 record.

He has elevated the performance of an already-talented defense. The unit leads the NFL with 18 sacks and eight forced fumbles and ranks second with eight interceptions, matching the total it recorded in each of the last three seasons.

The Bears defense ranks fourth in the NFL in total yards (294.5 per game) and second against the run (64.0 yards per game). The Bears are one of only two NFL teams that has not allowed a rushing touchdown and one of three that has not permitted a rush of at least 20 yards.

Asked what he has enjoyed most about working with Mack, Bears defensive coordinator Vic Fangio said: "Well, his play No. 1. But I think what I've enjoyed most about him is the guy does not have an ounce of prima donna in his body. He's a joy to be around. The other players like being around him. The coaches like being around him. Besides his talent and production, which everybody sees, he's really a breath of fresh air to be around, too, on a daily basis."

Mack is the first Bears player to win an NFC player of the month award since cornerback Charles Tillman in October 2012.