Sheffield United manager on Ivo Grbic, Sam Curtis, possible ins and outs before the transfer deadline and Mark Clattenburg

Croatian international Grbic, 28, who stands 6ft 5in tall - is set to join in a £2m deal after completing a medical.

Right-back Curtis, 18, has been brought in with an eye on the future, with one of Blades chief Chris Wilder’s main priorities now being to bring in a senior right-sided central defender ahead of next week’s transfer deadline - with Chris Basham and John Egan on the long-term injured list.

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, who has confirmed that midfielder Ismaila Coubaily’s loan departure from the club is imminent, said: "The specific positions we are after, we feel we are going to nail.

"We have lost two really influential players in the (right centre-back) 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."

Ex-St Patrick’s Athletic player Curtis - 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, whose side welcome Brighton in the FA Cup on Saturday, added: "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."

Grbic’s impending arrival would take the club’s number of senior goalkeepers to four.

Wilder continued: “Adam (Davies) is injured at the moment and we will see what we have to do in the next week. It possibly is ‘one-heavy.’

"We will make a call on that. We have three goalkeepers out of contract as well, so I think something we had to look at as well, looking to bolster that department."

Meanwhile, Wilder has hit back at Mark Clattenburg's controversial comments about his side and striker Oli McBurnie after the ex-Premier League referee slammed a decision to award the Blades a late penalty in last weekend's draw with West Ham.

Clattenburg used his national newspaper column to criticise the call to award after Hammers keeper Alphonse Areola challenged McBurnie.

Clattenburg commented: "If you know football, and you know Sheffield United, and you know McBurnie, then you know he is going to try to disrupt the goalkeeper."

Asked for his thoughts, Wilder responded: "I just think it's really ignorant in terms of the way we play.

"Criticism only hurts when it comes from people you respect, so I'll leave that at that. It's just a nonsense, clickbait.”