Loyalty is a casualty of the NFL's free agency system and it goes both ways. The player we love today is the player we root against tomorrow.
The players position is hey! Am I supposed to be loyal to your team or to my family? I'm making a living here and the other team is offering more incentives to play for them.
There is as changing dynamic in NFL fandom. Free agency, fantasy football, and social media have played a part in the shift from rooting for a team to rooting for specific players and following them around the league.
I would say that there is a downward shift in the entire concept of loyalty from the perspectives of both fans and players.
As for Gregory, I don't see him making a great impact for the Broncos. First of all, he got paid.
Secondly, the season is 17 games long, not 4. Five of his six sacks came during a four game block in the middle of their six game winning streak early in the season as did 11 of his 17 QB hits and two of his three forced fumbles.. Three of his four tackles for losses also came during that four game block. It was as if he knew he had done just enough to get a contract and skated the rest of the way.
As for the other 13 games, Gregory was out for five of them. His remaining productivity for the other eight games, which is half of a season, was one sack, six QB hits, one forced fumble, and one tackle for a loss.
Gregory played in three of the Cowboys losses in which he had a total of zero sacks, one tackle for a loss, two QB hits and zero forced fumbles. He was a total non-factor.
Gregory spent a quarter of the season playing at a Pro Bowl level, a quarter of the season hurt, and half of the season he was the Invisible Man.