Boro have bid £8m for the Dutch goalscorer but Groningen want £12m.
It has forced the Riverside club to hedge their bets in the pursuit of a striker to score the goals to put them in contention for promotion to the Premier League.
“I’m not so sure if it’s two bids or not, but we have put a bid in for the player. There is no hiding from that.
“I’m a straight batter but I can’t fib. We’ve put a bid in for that player, but we have bids in for two or three players that are ongoing.
“So hopefully we can see some movement on that front over the weekend, but as it is now, we travel to London with the same group we had last weekend, with the addition of Paddy McNair.
“I think we all understand it’s not how we would like it to look, and I’m sure it won’t be how it looks when the window shuts.”
Wilder has already stated his intention to sign another five players before the transfer window closes on Thursday, September 1, and is disappointment that the season will already be a month old by the time he has anything resembling a finalised squad.
After the 1-1 draw with West Brom last Saturday evening that exacerbated the need for a reliable striker or two, Boro head to a QPR side also harbouring ambitions to challenge for promotion.
“There won’t be a lot of changing in the group other than Paddy McNair coming back,” said Wilder.
“We’ve had a week to work with Marcus Forss which has helped.
“We’re still building and I believe we’re a team that will get better as the season progresses.”