The fullback is on the brink of completing a move from Championship side Barnsley after reportedly having a medical on Thursday.
Swansea City were also keen on snapping up the 25-year-old but despite having seemingly beaten the Jacks to the London-born, Wagner is not getting carried away just yet.
“Everybody knows I rate the player [Yiadom], we like him and hopefully we can progress something," Wagner said on Thursday.
“There is nothing to announce yet, but it looks like it is progressing.
“We already know we have some new faces and we are very lucky and happy to have been able to make signings early and have them work with us in pre-season.
“While he [Yiadom] isn’t signed for us, I don’t really like to speak about him because he is a Barnsley player.”
Barnsley initially rejected separate bids from Swansea and Huddersfield, and although the Jacks reportedly presented another offer worth £3 million, it is the Terriers whose second bid looks set to take the Black Star away from Oakwell Stadium.
Yiadom will become Wagner’s 11th signing of the summer as they kick off the Premier League campaign at Crystal Palace on Saturday.
A deal is likely to be announced on Friday.