Recent coaching hirings have shined a light on an ugly prospect: that the NFL is starting to set up its fight for a potential work stoppage in 2021 and a disruption of football that season, league sources told ESPN.

In coaching contracts negotiated in the past week, teams are addressing how much each coach would make -- or lose -- in the event of a work stoppage, according to sources.

Teams are trying to protect themselves and save money in the event of missed time, using different percentages for amounts of the football season that could be missed in 2021.

One league source told ESPN that he thought both teams and coaches are confident that there will be some type of disruption, and one of the first signs of it is showing up in the language of coaches' contracts.

These contract provisions were also seen in the lead up to the 2011 lockout 🔒. Take note. https://t.co/iiBry4MRey — NFLPA (@NFLPA) January 13, 2019

That language is also expected to appear in some player contracts being negotiated in free agency; in the third year of those deals, the current collective bargaining agreement is due to expire.