Substitution issue.

[JRutledge]

Tell me what you have on this play.

Home team has the ball is in the middle of the field. The visiting team is on defense and between downs is making multiple substitutions. After all the substitutions were apparently made, the visiting team (on defense) had 13 players on the field as the offensive team comes to the LOS to run their play. B13 runs off the field when he realizes he is not supposed to be there. B12 is confused if he is supposed to leave the field. B12 yo-yos back and forth around midfield and cannot decide for sure if he is supposed to be on the field. The offensive team QB has started his cadence and ready to start their play.

What do you call? Is there anything to call? Who should make a call if any? I would also like rule references in your responses.

Peace