Thanksgiving also signifies the start of hunting season, the time of year when NFL head coaches are put on the clock.

So start the speculation about the number of head coaching changes — it could be significant.

Since 1990, there have been, on average, 6.5 NFL head coaching changes on an annual basis, and it always seems to be 13 every two years. The fact that there were only four last season means there could be in the vicinity of nine this year. Three already have occurred — St. Louis, Oakland, San Francisco. And there may be plenty more to come.

There always is a surprise or two — Brian Billick in Baltimore last season, for example.

History says there will be six more head-coaching changes in the coming weeks and months. But either way, it promises to be a busy hunting season.