Substitution question / What do we have?

[NVFOA_Ump]

During a Team B timeout, Team A's offense huddles with 14-15 players on the sideline with the coaching staff.  R signals timeout has ended and 12 Team A players enter the field past the 9's and are getting in formation.  Team B is immediately matching up as a 13th Team A player starts in while almost simultaneously 2 Team A players head back out.  What do we have? 

[Legacy Zebra]

Team A may have more than 11 in formation as long as it is for no more than 3 seconds. So if they were there for 3 seconds or less, you have nothing. If more than three seconds before the 2 players left, you have a dead ball illegal substitution.

[NVFOA_Ump]

So how do we reconcile that with the AR that basically says once a Team A member has come onto the field past the 9 yard marks and assumes a position in the formation that he has become a player and must remain in for at least one play?    I can agree with letting the original "extra" player leave, but doesn't the "13th" player who comes in after the first 12 and replaces a player who was in formation and has not been in for at least one play violate the rules?

[Reverend30]

I think as long as you give B the chance to match the substitution, you're in the clear on this one.  As long as A makes the substitution within the 3 second window, don't go looking for trouble.