On Wednesday afternoon, Kansas City Chiefs backup quarterback Chad Henne was back at practice.

As you’ll remember, Henne injured his ankle (what is it with the Chiefs and ankle injuries this year, anyway?) during the preseason. The injury was going to require surgical repair, so the Chiefs kept him on the roster through the preseason’s final cutdown and then immediately placed him on injured reserve — moves that would make Henne eligible to return to the active roster after he had missed eight games (not weeks) of the regular season.

So how is it that Henne was suddenly on the practice field on Wednesday — when the eighth game of the season has yet to be played?

The answer lies in the minutiae of the NFL’s rules about injured reserve — rules that seem to become more complicated with each passing year.

While on injured reserve, an NFL player is prohibited from practicing with the team, but not from being involved in other team activities such as attending team or position group meetings. So while Henne hasn’t been on the practice field with the team since the season began, he’s fully up to speed with everything that has been covered in the quarterback room while he’s been on IR.

But in order for a player on IR to practice with the team, the team must officially name the player as designated for return from injured reserve. Once this happens, the player is free to practice with the team as if he were already on the active roster — even though he doesn’t yet count against the 53-man roster limit.

But there is an important condition for this designation. Once a player has been designated for return, the team must put him on the active roster within 21 days. If that doesn’t happen, the player returns to injured reserve for the remainder of the season.

As a practical matter, this means that a player could begin practicing with the team after missing as few as five games. But in order to avoid the risk that they will be forced to use a roster spot for a player who still isn’t ready to play, teams don’t designate players for return until they believe the player is within three weeks of being ready to play.

Furthermore, a team is only allowed to put two players on designated for return status during the course of the season — which means they are only going to do it for players they believe will be able to play within the 21-day window.

So how is it that Henne was on the practice field Wednesday afternoon — even though he hadn’t been designated for return?

That answer is pretty easy: the Chiefs simply decided not to tell anyone about it. The team made the designation sometime between late afternoon Tuesday and when team practice began on Wednesday; the designation was listed on Wednesday’s official NFL transaction report, which is released around 4 p.m. (Arrowhead Time) each weekday.

Now that the Chiefs have used one of their two designated for return options to bring Henne back, what does that mean?

Unless he surprises us with his performance, veteran backup Matt Moore’s days on the Chiefs roster are probably numbered. That’s likely true for rookie Kyle Shurmur as well. When Henne is ready to play, it won’t be difficult to predict which player will be cut to make room for him on the roster: Moore or Shurmur — or maybe both.

Whether it’s the rookie (or the veteran who could surprise us with his play in Week 8 and Week 9) will largely depend on the progress Patrick Mahomes makes in the next couple of weeks. If the Chiefs feel that Mahomes is coming all the way back, they could easily decide they don’t need to have more than two quarterbacks on the active roster. But if they aren’t sure, they could decide to keep both Henne and Moore for the final weeks of the season.

On the other hand, in order to get Shurmur back on the practice squad, the Chiefs will have to expose him to the waiver wire — which they might not want to do.

So like all circumstances of this nature, there are number of moving parts at work here. The only thing we can say for sure is that the Chiefs now expect for Chad Henne to be back on the roster sometime in the next 21 days.