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Why Field Yates likes the Commanders taking it slow with Chase Young (0:39)

Chase Young may not be ready for the start of the season. :39

1:05 PM ET

The Washington Commanders fired defensive line coach Sam Mills on Tuesday due to a "difference of philosophy."

Jeff Zgonina was a teammate of Mills' father in the football team. Zgonina worked for Mills the past two seasons.

Rivera didn't say what he meant by a philosophical difference, but said it was just some observations. It was a change I needed to make.

Rivera brought Mills with him when he became Carolina's head coach. Mills was elevated to the main role after Brady Hoke was fired. After Rivera was hired, Mills moved to Washington.

The father of Mills was in the NFL Hall of Fame.

Rivera's past with the Mills family made it difficult to make this decision.

Rivera has known Sam for a long time and he is a great football coach. He's done a lot. He helped us win a division title, but there were some things I wanted to change.

There were questions about the group's chemistry and willingness to play in the system as Washington's defensive line underachieved. A unit that had been used to a different style of play was not happy about that.

Rivera was worried that the football maturity of some members of this group led to bouts of selfish play.

Washington allowed Tim Settle to sign with Buffalo in free agency after releasing Matt Ioannidis. The Commanders made a second-round pick.

Jon Allen said it was sad. Coach Sam and I were making progress as a defensive unit. People need to remember that the game is a great one, but a terrible one.

Allen was surprised by the timing.

He said that nothing is unusual. The NFL will surprise you as soon as you get used to it.

It isn't my job to worry about that. I play football. We have a lot of faith in Rivera.

The players were told the news by Rivera. The defensive ends will be helped by a third-year staff member. Ryan Kerrigan, a former Washington player, will be here throughout camp.

Warren Sapp was assisting in practice. He worked with the defense in the spring. Rivera said that neither Sapp nor Kerrigan will take a bigger role.

Zgonina was a defensive line coach. Zgonina won a Super Bowl with the St. Louis Rams after being drafted in the seventh round.

Zgonina said it's always difficult. I've known him for a long time and he's always going to be a friend. I have a job to do and he has a job to do.