Do you disagree that most teams lose at least a few players for the year as the season progresses? Do we really need to go back and look at data? We totally can.
Just ACL tears, but the average is about 55 a year across the league, slightly more than half of which are during the season, the rest preseason. So that would average out to just under 1 per team lost during the year as the season progresses to a torn ACL. Obviously there are other types of season-ending injuries, like broken legs/ankles or torn achilles or certain muscle or ligament tears. Concussions and MCL tears (included on this chart) aren't usually season-enders, unless you're very close to the end of the season.
https://www.nfl.com/...ata/injury-data
Would be interested if there is more detailed info available. This was just the first thing I found.