Oakland Raiders quarterback Derek Carr did not expect Khalil Mack to be traded.
The Raiders sent their star 27-year-old pass rusher, along with a second-round pick, to the Chicago Bears in exchange for four future draft choices.
Carr told reporters on Monday the team have moved forward after they were initially surprised by the deal.
"It isn't what anybody wanted – I think that's clear," Carr said (via ESPN). "But it is what it is – it's part of the business … It's one of those things that happen. The hardest part for me is, obviously, you lose a good football player, but he's my brother, man. He's one of my best friends.”
Mack, the 2016 Defensive Player of the Year, was looking for a new contract and had been holding out of Raiders camp. The Bears made Mack the highest paid defensive player in NFL history when they inked him to a six-year, $141million extension after the trade.
Carr said Raiders coach Jon Gruden discussed the move with the team.
"[He] said what he said, invited anyone who needed to talk to him, open door," Carr said. "He understood that a lot of us were close with him.
"It didn't go away, because he's your buddy, but at the same time it went away because we have a game to get ready for."
Mack, a three-time Pro Bowl player, tallied 10.5 sacks and 61 solo tackles with the Raiders last season. He was originally selected by Oakland with the fifth pick in the 2014 draft.
Oakland open the regular season against the Los Angeles Rams on September 10.