Town's first-choice keeper was sent off for an alleged handball outside the area 20 minutes into the contest.
And that dismissal means the on-loan Liverpool stopper is set to miss the first leg of the SkyBet Championship play-off semi-final against Sheffield Wednesday at the John Smith's Stadium next Sunday - unless Wagner launches a successful appeal.
“I haven't seen the video again but Danny says he touched the ball with his shoulder, not his arms or his hand,” said David Wagner.
"If we can clearly see the referee made the wrong decision, then we will appeal."
Wagner, who has been asked by the EFL to explain his team selection after making 10 changes for last weekend's 2-0 defeat at Birmingham City, made nine changes for this game, bringing back most of his key men.
"What happened with Danny Ward is why it was good to bring in some fresh players for the Birmingham game," Wagner added.
"Joel Coleman played in goal against Birmingham and has had more minutes to work on his body shape and fitness."