Wagner also confirmed Jonathan Hogg is back in contention to lead out the side and praised the midfielder’s driving influence at the club.
Town, in 16th, are four points above the drop zone as they tackle the 12th-place Hornets, and Wagner believes Mounie can help provide a winning sting.
“Steve Mounie is a top class striker, I said this after pre-season,” commented Wagner of the £11.5m signing from Montpellier who has nine goals for the campaign.
“He is a threat; his link-up play with Alex Pritchard gets better and better and, hopefully, he will score some more goals.”
Town had worried that Hogg may miss the match after suffering an injury in the 1-1 draw at Brighton & Hove Albion, but the 29-year-old has pulled through and returned to training on Wednesday.
“Hoggy is our proper Terrier; if you have to create a player to demonstrates what a Terrier player is all about, then it’s him,” beamed Wagner.
“He has the passion and desire to make the hard yards and always changes his borderline.
“He’s a real leader on the grass.”