"If you're a coach coming into a new situation and this is a player that you covet and you really want on your team, there's no egos in this," the ex-Patriot tells TMZ Sports.

"I think you call the player and express your feelings and what you expect and what you need."

Remember ... Mack's whole issue with the Raiders stems from the fact that he and Jon NEVER spoke after Gruden got the head gig.

Willie -- a former stud pass rusher himself -- is perplexed by Gruden and the Raiders' role in the situation ... especially after the new Chicago Bear BEASTED in his first game Sunday.

"I understand there's two sides to the business," McGinest says.

"But, Khalil Mack, in my opinion, is a generational player that can control and impact the game."

For Gruden's part ... he tells ESPN the trade had to go down because, "Obviously, Khalil Mack didn't want to play here."