By Greg Gabriel-

(CBS) When you spend close to 30 years working in the National Football League, you see and are around a lot. I have had the opportunity to work with some great coaches and front office members like George Young, Ernie Accorsi, Bill Parcells, Bill Belichick and Tom Coughlin. When you work with people like that, you can generally figure out why things work and why things don’t work.

Granted, when I was working for Young in New York, the league was different. In my first few years with the Giants, there was no such thing as free agency. When free agency began, it was nothing like it is now; we had a process called “Plan B.” Under that system, movement was very limited, and most teams only gained or lost a few players. The system changed over the years to become what we have now, which is full-blown free agency.

It was free agency that basically drove Young from being one of the great general managers of all time. He was brought up in different type of league and could never really adapt to free agency.

The point I’m making is that the key to long-term success in the NFL is being able to adapt. Those who can adapt on the move to an ever-changing type of player and league are the ones who survive and have the most success.

The best I have been around in terms of adaptation are Parcells and Belichick. The success they have had is because they were able to adapt. They understood the rules, and they understood the players. They know what makes players tick, so to speak, and know how to drive and motivate the players to play to their optimum level.

Marc Trestman is a good man and he knows offense, but he hasn’t adapted to the NFL. Before he became the Bears’ head coach in January 2013, he was away from the NFL for nine years. In that time, the game has changed. Players are different, strategies are different.

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In 2013, Trestman’s offense did a very good job, but in 2014, defenses adapted and adjusted. The result has been an underachieving offense. Trestman didn’t have an answer to the adjustments.

Not only has Trestman struggled to adapt to changes in game strategy, but he hasn’t adapted to what goes on in the locker room. In talking to Bears players and former players, I keep hearing the same thing.

They don’t respect Trestman as coach and a leader.

They feel he worries too much about the little things that have nothing to do with football and not the most important thing, which is their performance on the field.

When Trestman was hired, he took over a veteran team on which most of the players had spent a good portion of their careers under Lovie Smith. They were used to doing things the way Smith did them. While Smith wasn’t a vocal disciplinarian, he was still strict — and the players respected that. At the same time, Smith let the players be themselves.

The players also had a leadership structure within the locker room. The leaders were mostly on the defensive side of the ball, but those players had the respect of everyone on the team. They were Brian Urlacher, Lance Briggs and Charles Tillman. They were the elder statesman, and the younger players listened and looked to them.

When Trestman came in, Urlacher was phased out and, according to the players, Briggs and Tillman were more or less pushed aside as the team leaders. This didn’t sit well with Briggs, Tillman or others.

Little joys that the players had come to like were taken away for a time. For instance, there was always music blaring in the locker room. That was cut out. It wasn’t until both Tillman and Briggs pleaded with Trestman that music was brought back.

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You have to remember, the locker room is the players’ sanctuary, and it’s where they “live.” Players want to feel comfortable in their room. If a coach wants the players to perform for him, he has to let the players have their own identity.

Another worry I have heard from players is the lack of accountability. While the players were told they were going to be held accountable for their off-field issues, they weren’t even held accountable for their on-field performance.

Players aren’t stupid. They know who is playing well and who isn’t. They know when someone earns a job or is given a job. When the wrong people are playing, players take notice and react. Usually the reaction isn’t good.

We can’t relive the past, but if Trestman wanted to succeed, he would have been better off not only getting rid of Urlacher when he did but also Briggs and Tillman. That trio was the bridge to the Lovie Smith era and if Trestman was going to have success, he needed players who were going to have unquestioned loyalty to him.

When we look at the events of last week in regards to the Aaron Kromer mea culpa to both the media and the players, we see how dysfunctional this franchise has become. In all my years in football, I have never seen a coach thrown under the bus like Kromer was.

If the powers that be found out that Kromer was the person who leaked the coach’s feelings about Cutler to the national reporter, it should have been handled strictly by Trestman in house. Having Kromer apologize to the players was a disaster. Kromer and the rest of the staff have lost all credibility and ability to lead the players.

If this staff had any chance of returning next year, it ended last week with those events. That became very apparent with general manager Phil Emery’s statement on WBBM before Monday’s game, when he distanced himself from the situation and made clear it was Trestman’s decision to retain Kromer at the moment.

We only have two more weeks before this nightmare of a season ends. At that time, changes will be made. What we don’t know is what the changes will be and who will be involved.

As I have stated before in this column, I believe Emery should be able to rectify his mistake of hiring Trestman. Whether that happens remains to be seen, but we will find out soon enough.

Greg Gabriel is a former NFL talent evaluator who has been an on-air contributor for 670 The Score. Follow him on Twitter @greggabe.