Sheffield United transfer latest: Blades close to signing Atletico Madrid keeper after bringing in international defender - with midfielder set to depart

Right-back Curtis, 18, has been brought in with an eye on the future.

The St Patrick’s Athletic player - who has made over 61 senior appearances and played for his country at under-21 level - was also linked with moves to Manchester United, Manchester City and Chelsea.

Wilder said: "Sam is one for the future, and we are looking forward to seeing how he progresses at Shirecliffe.

"He's a player who Keith Andrews knows well, and we think he will benefit from being in our environment.

"Of course, we spoke about players that we were signing in January as potential starters, but Sam is different and we could not turn down the opportunity to bring him to United.”

Meanwhile, Croatian international Grbic, 28, who stands 6ft 5in - is set to join in a £2m move after completing a medical and will provide a much-needed fresh option in goal.

Wilder, whose side host Brighton in the FA Cup on Saturday afternoon, said: “We are close to getting a couple in. So fingers crossed and those things are it’s happening as we speak.

"The big thing is when the window shuts, we are in stronger and in a better place than when the window opened and I believe we are now, with players coming back fit and the likes of Ben Brereton-Diaz coming into the group and a couple coming in over the next 24 to 48 hours.

"From a psychological point of view, our players want to see players coming through the door as well for their chances of getting results and having a successful second half of the season.”

On Grbic, he added: “He is (undergoing a medical). He is close and fingers crossed we can seal that deal."

Meanwhile, Wilder has stressed that bringing in another senior centre-defensive option, with Chris Basham and John Egan on the long-term injured list remains a big priority before the closure of the window.

The Blades have been linked with moves for several players including Everton’s Ben Godfrey - also said to be on the wanted list of Leeds United - Toffees team-mate Mason Holgate and Bournemouth’s Chris Mepham.

Wilder has also revealed that midfielder Ismaila Couilbaly will be heading out on loan to boost his prospects of game-time.

The Malian has made one appearance this term. In the EFL Cup game with Lincoln City.

Wilder added: "The specific positions we are after, we feel we are going to nail. We have lost two really influential players in their position in John Egan and Chris Basham and we are light in terms of right-footed centre-backs. I like that balance and the option of playing three as well.

"It (window) is part and parcel in football. It is an incredibly hectic period and there is a player going out as well. Koulibaly goes out today on loan.

“Getting players out is something we have to do to balance it and we will work through it to the best of our ability to work as hard as we can to make that group stronger.”