Before that Joel Coleman made an excellent penalty save from Lukas Jutkiewicz as Wagner made ten changes to the side which secured a Play-Off place at Molineux on Tuesday evening.
Other notable mentions were a first appearance on a Championship team sheet for 19-year-old midfielder Regan Booty while Chris Löwe, Rajiv van La Parra, Izzy Brown and Michael Hefele were all rested and didn't make the trip to the Midlands.
With Birmingham City ominously close to the drop zone, their relegation rivals may have felt it was unsporting for Wagner to make so many changes to the Huddersfield Town line-up.
The fact remains Wagner's men have not only earned the right to do so but also proven their 'second-string' is more than adequate opposition for anyone on countless occasions this season.
Roared on by a vociferous home crowd, Birmingham were sparked into life and were awarded a penalty minutes later as Hudson was adjudged to have brought down Che Adams in the area.
Former Town old-boy Lukas Jutkiewicz stepped up to take the spot-kick but it was well saved by Town keeper Coleman much to the anguish of the Blues crowd.
In an end-to-end opening exchange, a quick Birmingham City counter was then foiled and as the ball ran loose, Adams was given a straight red for a reckless lunge on Cranie to compound their previous spot-kick misery.
With so much at stake for the home side, the game descended into a tempestuous affair and despite the man advantage Town were unable to capitalise as Philip Billing and Jack Payne both had good opportunities to open the scoring.
But Birmingham weren't to be discouraged and took the lead through Jonathan Grounds as half-time loomed - captain Michael Morrison capitalising on some slack Town defending to keep the ball alive and find the full-back to head home with aplomb.
The interval saw Wagner make a tactical change in an attempt to assert their authority on the game; Holmes-Dennis replacing Nahki Wells as the side changed to a 3-4-1-2 formation with Bunn and Joe Lolley reverting to wing-backs.
Despite the change Birmingham still offered more of the attacking impetus and could have doubled their advantage as Coleman did well to deny Jutkiewicz one-on-one after the forward escaped the attentions of Hudson.
This time Dean Whitehead, who had moved into defence due to the changes, brought down Jacques Maghoma in the area with the referee once again pointing to the spot.
The hosts weren't to be denied a second time with Craig Gardner making no mistake to send Coleman the wrong way to double their lead.