Inelligible Player?

[qcumpire]

This situation occured in a game last week.

Offensive team has 10 players in the huddle, the 11th player is on the field but has a minor leg injury. When they break the huddle, the injured player is headed for the sideline. The offensive coaches are yelling at that player to stay on the field. The player does not make it to the sideline and comes back toward the middle of the field. He does make it inside the numbers and lines up in a legal postion. The play is run and goes for a touchdown.

The defensive team then complains that the player that started to leave the field is an illegal substitution, saying he went toward the sideline and was not in the huddle.

Thoughts, opinions?