Outside linebacker Khalil Mack was traded to the Bears for a reason, Raiders coach Jon Gruden told ESPN.

“Obviously Khalil Mack didn’t want to play here,” Gruden said before his team made its debut Monday night. “That’s what’s being missed here. He was under contract. … He never showed up for an OTA, never showed up for training camp, and it was obvious he wasn’t gonna show up for the season.”

The Bears aren’t complaining — and not just because of Mack’s dominant performance Sunday. Staley said Monday that he’s a good example for their younger players.

“He’s a really vibrant guy,” outside linebackers coach Brandon Staley said. “He’s really got an energy about playing and practicing and training.

“And so I think that’s the biggest thing, is his example. The way he takes the field during practice, the way he is in meetings. For him to get here seven days ago, take a full game plan and then apply it to really good opponent just shows you — to younger guys, whether it’s offense or defense — what can be done. And what’s expected of a guy that’s of his caliber.”